How many miles do you have on it? I have a 400E and around 160K the engine wiring harness went bad. This is pretty much garunteed to happen at some point with all of these wiring harnesses. Many have resulted in fires and accidents but MBusa won't admit it. The wiring harness can cause a slew of problems. For me, the car would only start some of the time, and it started stalling as well, and eventually it would not come back. Once replaced, the car runs fine. I would look into the wiring harness though, there are numerous threads on the board, and you might come across someone with similar symptoms.