Why does he stare at me a lot?

So, I know this guy, and I catch him staring at me a lot. He is really popular and stuff, he isn't shy at all, but he always looks away when I catch him. I honestly barely know him, and I'm not sure he even knows my name. But he was with me when I lost my wallet one day and seemed worried. And we had a pep rally and were sitting in the bleachers a week ago, and he sat in front of me. He sort of leaned back against my knees, but I don't know if he was even conscious of it. I was just wondering, since I barely know him and he is crazy popular and stuff, why might he do this? Thanks!