i have a 2000 ml 320 cranks but will not start, i can drive the vehicle for about 15 min. and when i shut it off, say go into a store or friends house for about 20 min it will not start when i come back wait for about an hr or so i t will. any help will be appreciated

 

I had a similar problem with my 99 ML320 and it turned out to be the crank positioning sensor. After replacing it, all was good.