When my oldest son was little, he used to bang his head as well. He would get on all fours and bang his head on the floor. I hated it. I told his pediatrician about it, and she told me he was just doing it for attention, and to ignore it, and he would stop. He did not stop. What did make him stop was me finally walking up the steps into his bedroom, and scolding him harshly. He got scared, but he never did it again.
Because of his age, I wonder if he's bored. I hope you do not have him in day care. I suggest you try to keep his hands active in age-appropriate activities, like pat-a-cake, peek-a-boo, or "Sooo big!" touchdown arms. Will he crawl after a ball? "Dance" to music? Find a book or website for ideas. If you haven't already, look into "mommy and me" classes to help keep him stimulated and you connected with other moms. Good luck!
My daughter is 13 months old and initially started banging her head when she was angry/upset. If I put her down on the floor, for example, she'd just bang her head on the floor 2 or 3 times and cry. She doesn't do it anymore but at the time I was quite worried that it was a medical/behavioral problem.
I think you should speak to his pediatrician and see if he/she thinks it might be normal or if there is a medical or behavioral reason he's doing it. He's still very young, it could be just a short phase he'll go through but it never hurts to check.