Tv antenna turns by itself
If the rotator has a separate power injector in addition to the controller, make sure that is unplugged also. If all power to the rotator is cut, and the antenna is still rotating on its own, there are 2 possibilities:

The rotator motor or its gearing could have gone bad. Something could have broken from use over time or some extra strong wind that now causes that much slop to be in the mechanism. Probably the only fix is to replace the rotator. It seems that the recommended course of action would be to try and find a new old stock type model, as they have a much better reputation than the ones made today. I can't vouch for this personally though.
The clamps holding the antenna to its pole or the rotator to its pole could have loosened over time. Just get up on the mast and tighten everything up again.