190e 2.6 won't start. Help!

OK, here's the deal. It's an 87 190E 2.6, and have posted this before as a "stall problem". Now it's worse. The car starts fine when cold and runs like OK, though the idle is a little shaky. If I turn it off and try to restart it while warm, it won't start. It just turns and turns. I can try to start it numerous times, letting it turn over 5-10 seconds at a time, and it won't start. An hour later it starts right up. Obviously I don't always have the luxury of waiting an hour. What does it sound like...the overvoltage relay? I checked the 10 amp fuse on the OVP and it was OK. About 3-4 years ago, the ignition coil was changed.

Help!!