Does Justin Bieber have a nervous habit?

I was so excited when I got to hang with Justin on the set of the MTV show Silent Library. I was standing just a few feet from the Biebs, and every time the director said, "Action," Justin would take off his hat, shake his hair, and then place his hat back on. He kept doing it throughout the entire scene. But the minute the cameras stopped rolling, he'd would stop. After watching several takes, I realized that his hair shake is his nervous habit! Aww!