I think the first answer is the one that fits. I confess to being a 'starer' although I really don't mean to be so! I am fascinated by people, and I am blessed with a rather intense stare, which to me is simply observing, but has got me into trouble more than once! I think people are probably just distracted, and you may find that when you move, their eyes don't follow you at all. If you try and avoid staring back - which makes things worse - and simply accept it as human nature, the phenomenon will probably cease to bother you.