What's wrong with your cruise actuator? Is your car jerking occasionally when you are on cruise, whilst going downhill?
I had the problem previously and I sent it for an independent MB Tech to take a look, and suspect the cruise actuator's fault. He susgested to change, but I did not.
I cleaned all the throttle linkage, and relube with ATF. The jerking is gone, and my cruise is working as good as it can be.