Car cranks up but immediately shuts off

Mine was a bad key fob believe it or not. I went to the store, shut it off...came out and it would start right up and then kill. Over and over same thing. My son researched on line and found the answer. I ordered a new key from the dealership and it started right up and no problems since. Good luck.

Sounds to me that this is a chronic problem and you have never addressed it. It's time.... It could be anything from a faulty fuel pump relay to worn out ignition switch and I don't have any information from your message that's helpful. I recommend you get it to a MBZ expert to diagnose it. If you want to find a specialist, here's a directory link for you: https://repairpal.com/mercedes-benz-repair-in-washington-district-of-columbia