How do I avoid making female coworkers uncomfortable?

This depends a bit on the country and culture where this is happening but if this is a US/Europe location I would reach out the HR with something like this (in writing).

I am very sorry that I made someone uncomfortable. That was certainly not my intent and I have no idea what I have done to trigger that type of reaction. I did treat them the same way as I do everyone else and I'm not aware of anyone taking offense. Can you please let me know what specifically is the issue? I'd be happy to adjust my behavior to make them or anyone else more comfortable but at this point I really don't know what to change. Can you please provide guidance and actionable feedback?

This will either bring out details on a specific incidence or pattern or they may stall you. If they stall, keep repeating "There is nothing I can do unless you provide details of the complaint. So either please provide actionable feedback close the issue".

See also: https://www.youtube.com/watch?v=cHdgdo1g8iA

How do I avoid making coworkers uncomfortable when I think maybe my presence just makes some women uncomfortable?

You can't unless you get some real data on what the issue here might be. You currently assume that this is related to the co-worker being female and younger, but you have no way of knowing. It could be something completely different, so it's important to find out.

Keep an open mind: it's entirely possible that you ARE doing something that makes them uncomfortable, but you are simply not aware of it. That happens more often than you think.

I had to deal with situations like this more than a few times and I have seen pretty much all shades: clearly warranted, borderline, completely not warranted and anything in between. In one case it turned out I was the culprit myself. I just wasn't aware of it and mortified when I found out. Good learning experience though.

In addition to @JobSeptember2020's comment that she may have thought you were staring at her, looking at someone else's work can feel like you don't trust her.

Plus having someone lurk behind makes many people uncomfortable.

Unless she asks for help, don't intrude on her space, and don't stare at her screen or at her. Focus on your own job and trust that she is doing hers.

If you want to voice a friendly "how's it going, is there anything you need from me", do so from a greater distance.

Personal space assumptions vary a lot. Err on the side of standing farther back. Better to be a bit standoffish than intrusive.

Afterthought: if there's another woman in the department whom you are on good terms with, it might be worth telling her that you have had this problem, and asking her to keep an eye on you and tell you if she notices you being unintentionally rude. She may have heard what the concern was, and even if not she may be more likely to notice it than you are, and more willing to tell you than the youngster in question.

If you look at my monitor intensely, I don’t like that at all. I might tell you by asking “Is there a fly on my monitor? If not, why are you staring at it? Don’t you have anything better to do?” I dislike it, but I would make sure you feel bad about it, and not I.

But it seems you are doing this to a nineteen year old girl. Who may have been brought up to be polite. She feels just as bad about it as I do. Thirty years from now she would ask about a fly on the monitor. Today thats not in her repertoire of responses. Going to HR is in her repertoire. What you do would make me feel uncomfortable, but I would know how to turn that back on you. She might have told a 25 year old colleague that you make her feel uncomfortable (which in fact you do) and got advice from there.

So I strongly recommend you stop looking over her shoulder, especially from a short distance, and stop staring at her monitor. People don’t like anyone behind them, and other people would have stopped you without HR.

To me, when you said "I did look over her shoulder to see the schedule a couple of times", I immediately think that is what is most likely to have crossed the line into uncomfortable, and as I guy I think you crossed the line. At worst interpretation (and to me, the situation that it most comes across as) it appears you were trying to look down her shirt/chest, slightly less creepy would be if you were trying to smell her, or that you're getting too close to her and invading her personal space, all of which don't come off well...

The fact you said you did this a couple of times is what really puts up the red flags as the likely culprit for what you did. A lot of people don't like to report others, but if you do it multiple times many people will eventually speak up and report it. Unless there are other things you did that you left out of the post, it seems that was the most likely culprit. Don't look over girl's shoulders, in the future.

How do I avoid making coworkers uncomfortable when I think maybe my presence just makes some women uncomfortable? Aside from my personal life I'm not sure what I did exactly that made this woman uncomfortable.

Is this the only instance, or have there been other reports and incidents over the years?

When HR comes and says you're making someone uncomfortable, out of the blue, the natural response is to ask what on Earth they are talking about and whatever do they mean by it exactly.

That said, it's possible for people to misinterpret harmless behaviour, or to feel uncomfortable because of uncertainty about the underlying motive.

Is it possible you're just supplying too much friendly attention, which is neither called-for nor reciprocated?

There may be nothing untoward about having more interactions with a particular person if your work brings you into contact with them, compared to how many interactions you have with colleagues who you need to encounter less for work purposes.

But exchanging pleasantries with a colleague doesn't always mean you want a half-hour conversation.

In other words, there may be no behaviour that needs to be changed, the interactions just need to be more moderate in length and more work-oriented?

Some people - perhaps especially teenagers - also have a keen sense of generational differences, and neither want to interact with decrepit elderly nor silly youngsters, and cannot see why anybody else would either. Certainly 30 years difference will mean you have few touchstones in terms of everyday pop-cultural experience.

The very fact of your significant age difference may therefore mean significant social interaction beyond the necessities is unwanted.

Ah, you've run into a perfect storm of the workplace, the post-MeToo era, and young people who are more liking to bark about feelings in the workplace than to recognize that the workplace is not a happy-go-lucky campfire hour. It's disturbing to recognize that you also are working with a human resources department that isn't transparent either.

In light of all these factors, I would personally avoid direct interaction with this young lady altogether. CYA. I think it's justified in your situation, in that your HR people want to tell you that you're a problem without telling you why. So if you have to deal with her, send email or use an instant messenger where all of your interactions can be documented. Don't exchange pleasantries if you see her. Don't sit near her in meetings, if it can be avoided. Don't even look her in the eyes if you happen to be facing her. Keep your interactions to a necessary minimum.

This kind of stuff is a predictable outcome of the things I mentioned above. I remember reading about male managers who started refusing to meet with female reports in private because of the same thing, or who would lean toward only hiring their same gender. All of this was to avoid exactly what you're experiencing now. If anyone who you work for has an issue with what you're doing, you can just point the finger at your encounter with HR, and go about your business.

It sucks that this is where we're at, but it's where we're at.

Some good answers already. My take is that this lady has an agenda. What it is doesn't matter. Your response to HR should be as brief and non-committal as possible. You're creating records.

I would tell HR I have no idea what they mean, and could they clarify with something I can work with. Then leave it to them to respond. There's no point trying to work it out and creating any wriggle room for misunderstanding or skewing whatever you say.

I'm going to be blunt, and it's going to make some people mad.

So be it.

This person is looking for a lawsuit, or more accurately, a lawsuit settlement.

She is using you as her foil.

You need to tell HR to get her out of your area immediately. You cannot be near her. You can NEVER be alone with her. If you have to work with her at all, insist on a 3rd party being present, preferably female.

Stop ALL non-work-related communication immediately. You have NOTHING to say and NOTHING to hear from her outside of work-related information.

These people are toxic, and they destroy people's lives with no concern whatsoever beyond the payout they're anticipating in the settlement.

Your HR knows this, but they can't say this.