I have a 2001 Mercedes E430 4matic and I am running into an issue where if I put the key in to the ignition, sometimes the car will start, sometimes it won't. When I run into the issue of it not starting, I leave it alone for about 30 minutes and then I come attempt to start it again. It is not a battery issue, there is plenty of power. Help.

 

Not starting, meaning it cranks for about 15 seconds and then stops cranking? When the engine has warmed up on a prior trip? If yes to both then - Crank Position Sensor. Located at the back of the engine, inserted in a while above the flywheel, held in by a torx fastener.