Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
Hi, it sounds like your key may have gone bad. Do you have another key that you can try?
You would need to order a replacement key from the Mercedes dealer. You can also try disconnecting the negative battery cable for an hour then reconnect the cable and see if it will start and stay running. If that doesn't work you can try disconnecting the cable for 24 hours and try it again.