My Mercedes Benz C280 petrol automatic is 28 months old with 8,500 miles on the clock. Recently in the very cold weather, before the engine has fully warmed up it has developed a tendency to suddenly rev up on its own accord. This happens when the car is stationary, in gear, and ticking over; out of the blue the revs shoot up from 500 to 750/800 rpm then settle down again quickly. This is disconcerting even when I have my foot on the brake. It is however, frightening when my foot is not on the brake and the car moves. Unfortunately, I have so far been unable to re-produce the effect for my local dealer, and as all his machines say everything is operating properly I am not sure I am believed. He has at least now agreed to refer to Mercedes Benz. In the meantime, are you aware of other examples? Or, have any suggestions that may assist my negotiations with MB?