Mercedes Repair Questions? Ask a Mechanic for Answers ASAP
to get an intermittent start like this I'd say its likely that the crank position sensor is faulty
or the wiring to it is corroded or damaged
if this is Ok then also worth checking the connections to the fuel pump for the same reason - unplug each in turn and give them a good squirt of switch / contact cleaner - Not WD40
and also unplug and inspect the main power relays and fuses for signs of overheating or corroded terminals - so the ones for the ECU and the fuel pump
And also unplug the wiring loom connections in the engine bay one at time and inspect for corroded or recessed pins.
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