For the past several months, when I turn the key in the ignition to start the car, nothing happens. No noise. No engagement. After 2 or 3 tries, which involve removing the key and reinserting it, it will engage and start. Yesterday, I ended up cranking the key 50 times or more before it finally started. Today, it fired right up, but after driving for 20 minutes and sitting at a light, it suddenly died while in drive. I put it in park and tried to start it. It did not start. After a couple minutes of fidgeting with the key and turning it over and over, it finally started. What could cause this?

 

I would say it was the ignition switch, except for the dieing while driving. that is puzzling. otherwise I had a similar problem on my sl and turned out to be the switch

 

maybe fuel / fuel filter.

better check the fault code.

 

Or CPS and Cps (Crank position sensor and Cam position sensor)

 

Spoke to millerpim and turned out to be a problem with the K40 Relay Module which her mechanic then replaced.

After doing some searching on the web, I came across Bazzle's excellent guide to repairing the soldering on this module at:
http://www.slkworld.com/slk-r170-gen...ay-module.html

I performed this work about two months ago andmy intermittent problem has not occurred since!

Thanks guys!