Normal from what I have seen with mine as well. Advanced auto pilot relies on waypoints projected out in front of the boat, in waves and rough water your boat is moving out of position more than you realize I believe.
The motor is compensating for the movement. You see the side to side action because the base of the motor is moving out of position in relation to the head of the motor so it turns to compensate for the smallest misalignment. Very accurate system from what I have seen with mine so far.
One other thing than can cause unnecessary corrections would be a weak gps signal. You can check that by the signal meter on the handheld display.
I absolutely love the ipilot and terrova. They hit a home run in my book so far with this system. I have been telling my friends this is the best thing to come out for a boat since the sonar.
Hey Minnkota how about a sponsorship