Re: He's hitting himself in the head!
My DS likes to bang his head against the walls or whatever is around. He will accidentally bump into something and then do it again and again deliberately. He's kind of slowed up on this a bit since there's lots of exciting stuff going on in his little world (lots of walking, talking, etc.). But for a while we thought he was going to need a padded room or something!
I think it's really common especially with boys for some reason (DD never did anything like it).