The transmission keeps slipping on my 2002 Mercedes-Benz C-Class. Do you know what could fix this?

If the transmission is working properly between bouts of slippage, then it’s reasonable to think that this could be an electronic problem rather than a mechanical one. By turning the ignition off and then restarting, you’re effectively resetting the computer that controls the transmission. That’s why the gearbox comes good for a period before reverting to its old tricks.

That’s on the surface, anyway, but the problem could also be within the torque converter or something intermittent inside the actual gearsets, clutches, bands or valve body that is giving the same set of symptoms.

Ultimately, this is probably going to require a trip to a transmission specialist who will be able to identify the cause more accurately. In the meantime, though, there’s something you can try that might reset the transmission more permanently. On this model Mercedes-Benz, there’s a specific transmission-reset procedure that should take the gearbox back to its original factory settings. If that’s the case, it might fix your problem, but if not, then you need to call in the experts.

The procedure starts with getting in the car, closing all the doors and turning the ignition key to the on position, but not actually starting the engine. You should have all the dashboard lights illuminated at this point. Then, press the accelerator pedal right to the floor, making sure you can feel that the kick-down détente has been activated. Hold the pedal all the way down for at least 60 seconds and then, without releasing the accelerator, turn off the ignition. Don’t open the door and don’t remove the key from the ignition. Now release the accelerator and wait five minutes before starting the engine and going for a test drive.

Good luck.