Interesting bahaviour. When I first watched the clip you have posted, I thought it's as if he's got a pressure point on his head or neck, and it's a relaxtion method to ease that pressure, much like a human uses massage, so I looked it up. The same clip appears on youtube, and one comment underneath the video, claims to have read his story, and it is reported as anxiety - which sort of makes sense, if you think of what I first thought. Whether it's true or not, no way of telling.
