Happens in all missions, in single as well as multiplayer, in 1st and 3rd person views, whether hosting or playing somebody else's server, and even if I start using the editor's preview option. I have no joystick or any other control device attached to my PC...only a standard mouse and a standard keyboard. I am not using Track IR or any other type of head movement tracking device. I don't even have a webcam on my PC.