Why does he act so strangely?

There's this guy at school who will spend weeks not talking to me, than he will come up to me one day and chat my head off. He isn't an extremely social person, in fact, he's somewhat shy. The only times I've ever actually seen him smile is when we were discussing wars or talking about various Mel Brooks/ Monty python movies (etc. Etc.) I also caught him looking at me from across the English room once. Whenever we happen to be walking near eachother in the hall he Either speeds up really quickly, gets uncomfortable, or starts talking about random things. Im pretty sure he doesn't "like" me, but his behavior is just confusing... Were also both band geeks in AP cles who are obsessed with frank Sinatra... Just sayin...