My new C230 Kompressor Sport Sedan has a very noticeable flat spot in the acceleration when coming from a dead stop or when just accelerating from slow speeds. Often, between 5 and 20 MPH, while accelerating, it acts as if you had just taken your foot off the accelerator. When you work the pedal up and down, it finally "catches" up and resumes accelerating. I have two of these cars, so it is not associated with any goofy thing that I am doing because it only happens with this car. It is now in the MB shop for the third time. They can't find the problem because it apparently doesn't show up on the computer. Any ideas or similar problems that were remedied?