lol.. no I think it is normal. Mine used to bang her head onto the floor when she had a fit as early at 9mo. she had a constant bruise on her forehead for about a year. finally she grew out of it.
my 3 year old son often does that dragging of his head when we are at the beach. I think it is just a sensory experience. everyone laughs and he doesn't even notice because he is so intent on what he is doing. it is strange I know. people look at me like I'm the crazy mom that lets him do it. but really.. he must be testing something in his little head.