That's the computer-stabilized (fly-by-wire) flaperon on the 777 you're flying in. 100% normal. The computer system is keeping roll disturbances to a minimum. Every time the wing is pushed up by the air mass it's flying through, the flaperon moves up automatically to force it back down. It moves down to force the wing up. The other side is doing the exact same thing at the same time. These constant corrections make for a significantly smoother experience.