My father, 57, shakes his head while watching television and occasionally when talking with someone. At first we thought it was because he disagreed with what he saw on tv or what he heard in conversation, but now I notice it daily. He does complain of headaches and takes Excedrin Migraine daily. He has recently been to his primary care physician and stated everything is normal, but I am not sure if he realizes the head-shaking, so I doubt he asked his physician about that specifically.