Trouble starting


I have a 1996 mercedes c3000 and it has trouble starting after sitting for a few hours. It starts fine after its been running but after a few hours of being turned off it doesn’t start. I’ve taken it to a couple of mechanics who seem to initially fix it, but after a few hours it doesn’t start easily. Any suggestions?

Three test need to be made while it’s malfunctioning: spark, fuel pressure and fuel injector voltage. The motor is not getting one of these when it refuses to start. Get it to malfunction right in front of a good mechanic.