My 18 month likes to hit. He also will push other babies heads down if there crawling. It makes me feel like hes violent. Although he seems to do it for attention he will run up look at you and real quick do it. Trust me attention that is something he gets plenty of! My nephew would do the same to my son with his head. So it is a learned behavior but it upsets me. My son is so loved and loving back I cant even get him to sleep without me. Yet another problem. But I know what i need to do for that just not ready.
There are great children's books which teach children socially appropriate behaviors and even more on how to identify and express their feelings in appropriate ways. I suggest getting them in his age level and reading up on them. Look for games of the same online or in the bookstore. Remind him hitting is not allowed and do make sure no other child is doing unto him. The sleeping thing he will grow out of this is another matter.
M Kay Keller