Hello,
Thank you for the information provided. I had very similar issues and it was my CLP/SSM. As many people here will tell you it is a waste of time to take these to the dealer anymore. A independent Mercedes shop would be a better bet there are a list of ones on this forum that people have had good dealings with.
I would see if any one in your area would let you borrow theirs. If not they are on ebay used and Needswings sells them new but they are non returnable due to them being special order.
I would also check and see if the headlights and dome/map light stays on after you get out of the car for about 40 seconds.
It may be as easy as cleaning those connections and connectors with alcohol I always use a non metallic brush to clean electronics then letting it dry and reassembling.
The tail of the dragon meet is coming up soon. If your not too far there will be 70ish crossfires there and a lot of people who love to help out.
Please follow up and let us know what the solution is.