I have a similar problem with my 91 300SE. Only on ocassion. It's like the accelerator pedal is not connected. I've also noticed that if I hold the pedal down it will eventually downshift and then accelerate briskly. I've done a lot of reading and many people have/are experiencing this. From what I can tell there is no silver bullet to fix it. It is dangerous, causes you to lose trust in the car, and worst of all it makes you envy your neighbors driving the the ever reliable Toyota's and Honda's.....