The car will not restart, a diesel motor will not run on petrol (gasoline). The car ran until the diesel in the fuel lines was used up and when the petrol replaced the diesel fuel the car died.
Is there an auto shut off? I say no. An auto shut off means a sensor would have to know the difference between gas and diesel fuel and cut off power to the fuel pump. It could be done, but I’m not aware of any cars and trucks that have one. The car isn’t running because of the petrol.
The fuel petal feeling disengaged is just that a feeling. This car has a “drive by wire” set up, there is no mechanical linkage to the fuel petal. It is an electrical potentiometer on the petal and small motor at the throttle body and the two are connected via a wire.
The car will not run so it will need to be towed to a mechanic. A MB dealer knows the car best, but a good shop should be able to handle it.
What is the best case scenario? Remove all the petrol from the tank and add a few liters of diesel fuel. Disconnect the fuel line at the motor and run the fuel pump to remove all the petrol from the fuel lines. Change all the fuel filters (the petrol will degrade the filters). Reconnect the fuel line and see if the engine will start. If it does it will be rough for a short time, but should smooth out in a minute or so. If it runs but not smoothly go to worst case scenario.
The worst case is there is significant damage to the fuel pump, or fuel injectors, or fuel pressure regulators, some or all. Even worse would be damage to pistons and internal mechanical parts. The lack of major noise and knocking as the car died tells me that internal damage isn’t likely.
Petrol is a very different animal than diesel fuel. Petrol can eat away and degrade seals and parts that tolerate diesel fuel with no problems. That means the faster the petrol is cleared out of the system the better.