21 month old baby

I have a concern, I have three kids and my youngest is always banging his head either when he's mad he will come towards you and start head banging you or even when he is just watching TV his banging his head back and fourth on the couch. He doesn't want to talk either he says maybe 3 words but he rather yell. With my other kids I've never had a problem with this they would talk before 2 years old. so I'm getting a little concern. Has anyone experience this with their child.