1999 Mercedes C280 dies without warning and then starts after vehicle sits. At least that is what it did. Now it won't start at all. It started when I would start the vehicle and it would idle rough until I turned it off and started it again. Then it idled smoothly.

If you have a carborator it is shot - If it is fuel injected than you have need to have your heads cleaned or replaced. If it doesn't turn over at all I would start with your starter. Your distributor can also cause this as well - I had to replace all of the above, minus the carborator and it fixed my problem - Was like a new car afterward.