Is my 21 moth old nomal or should i be concerned?

Noah is my 21 month old son we are concerned about. He doesn't say much only uses about a 10 words constantly and never together he does respond to his name and simple commands like no, and sit down, come here he will pull us to the door when wanting to go outside and to his cup when thirsty but doesn't point just wines. He understands conversation and will respond with babble if you ask him a question. He laughs when you laugh and smiles when you do. If you talk to him he will respond only with babble. Sometimes his babble seems if a form of a question. We are concerned about autism. As far as abnormal behaveurs he loves wheels and things that spin has always been infatuated with them and will lay on the ground to watch them spin on his cars. Should we be concerned plz help?