I have the EXACT problem with my 2007 SL550 with no warning light, will not start. I don't think the problem was clarified. When turning the key or pressing the keyless switch, the system begins the start cycle, but what ever it does stops after 2 turns, or solenoid actuation...Im not sure, but then nothing, repeated tries yields the same result until suddenly, the motor turns over and starts. Ive already had the crankshaft sensor replaced. Car runs GREAT both before and after problem event. A new starter was tried also, but problem persists.