I get this in shopping centres and supermarkets; I feel a sense of panic when Im shopping alone and Im constantly consciously thinking "dont approach me, leave me alone, dont speak to me, please just act like im invisible and not here." Its easier if my wife or one of my kids (not really kids now, they're grown up) is with me and they can handle all the interactions for me.
One of the earlier contributors to this post made me smile when they said how it can be additionally scary if the person who is approaching you is a police officer or authority figure - welll i totally get that, of course, but it can be pretty alarming when you are that police officer, in uniform, entering a shopping centre as part of your job to deal with something you have been called to ... and you are still saying "dont approach me, leave me alone, dont speak to me, please act like Im invisible and not here." Cops can be aspies too, although I would guess most of us are not. Life is strange.