I had simular problem with my 1993 300e. Towed to the machanic - off the tow truck started right up. Mechanic had it for two weeks - started all the time . Finally drove the car home . Next day no start. Than the help of MB forums I was cheking thing out under the hood. The top of the OVP relay I had a broken fuse. Changed the fuse, now the car starts all the time. PS. I ordered a new OVP relay