That is not normal. With my P4 I have seen one or two twitches like that with the camera pointing straight down and changing the movement direction, but nothing at all like yours. I would think that your gimbal is malfunctioning and would need to be sent in for repair.
My p3s does the SAME exact thing. I know the 4 is a different beast but same exact shake. Wish I knew why. Seems to be worse at higher altitude. Hope you get it figured out!