>>723928415
It's not a nervous thing, it's just non-verbal tourettes (tics.) As someone who has a slightly more relaxed version than his, it started to show signs all of a sudden when I was in ~6th grade or so.
Even in his early videos you can still see him roll his eyes upwards a bit (I do the same thing.) Probably just cut the sections where it was really bad and did some re-takes, I'd imagine.