Asked if im okay

I'm in college. I was sitting at my usual spot in the open area but this time I was there for several hours. Some girl comes up to me and asks if im okay because she saw that i was sitting there for awhile. I told her I was ok. I know it doesn't seem like much but it threw me off and is weirdly bothering me because I was just sitting there, on my phone, scrolling or whatever and suddenly someone comes up and asks if im okay? It made me weirdly self conscious about it now but Idk. Like what was i doing that made her ask that?