I have a 98 S420, same issue, but starts. If it were a key the car would not crank. I've been thru that issue with a different benz so have other friends. I also notice my power is not up to par. Takes putting the pedal nearly to the floor for it to take off with authority. Plugs, fuel system OK. I'm leaning toward cam sensing? Anyone with experience on this? It would explain both the prolonged cranking to start, and the lack of power.