it happens to me sometimes if i am standing in a line or sitting on the bus. Even if they glance at me it weirds me out if they are in such close proximity. Whenever I'm in a crowd of strangers, i usually just choose something to focus on or look downwards. I never understood (maybe cuz I have SA and am too scared to be that hyper-aware) why someone standing/sitting 2 feet from me would look at me sideways. Kind of weirds me out.