Is it a personal space thing or purposeful thing a person does?

So today at work I was talking to one of the employees and for some odd reason I felt very awkward like embarrassed really. I don’t know if its because he was standing fairly close to me, the positioning of his body or the way he was looking at me but I really thought I should walk away because it the feeling made it seem inappropriate to be there talking to him. Part of me felt like he purposefully did something to make me feel uncomfortable (cant pinpoint what) but the truth is our conversation was completely innocent (about working a lot of overtime) and he wasn’t any closer to me then many of my peers have been in conversation and I’ve never felt like that with any of them.

Do you think that its the invasion of acceptable personal space that causes the type of discomfort I explained or something a person intentionally does to invoke a feeling or do you think its something else all together?