Hello again. I am trying to get some more info before I take it to the dealer so I can keep from getting ripped off. Here is a little more information. The times that it has died it had only been running for about 10 minutes. Both times that it died, it was when I stopped. After it died, it would crank but not fire up at all. The last time it died, it took about 20 minutes before I could get it to start. After it finally started, it ran perfectly.
I have tried all 3 keys and it did not make any difference. Someone at another dealership that Mercedes roadside assistance called suggested that it could be the "crankshaft position sensor".
I hope this additional information helps. I will be taking it to the dealership in the next couple of days, but if there are no codes and it is running I don't think they will have a clue.
Thanks again everyone for all your help.