Thanks to everyone who replied.
Master S.M.C. - no other problems, he's with 1 other rooster and 15 hens. He is the only one doing this.
notsooldmcdonald- no frostbite. But he does have battle scars from the other rooster. They both have scars, but he is the only one with the head shaking...
One of my 2 roosters has been shaking his head side to side for some time now, seems to be getting worse. It's not a constant thing, but he does it often. No other symtoms. Any ideas?