You problem sounds exactly like the problem I had with my 1991 300SL. It would run fine and then after parking the car for a few minutes, it would suddenly not want to start again until I waited 5-10 mins then it would run. It turned out to be a lose crankshaft position sensor. Search for my post on the subject. Remove, inspect, clean, and re=install the sensor. Better yet, if it's a very old one replace it. Hope this solves it.

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03 CLK430 Cabrio 211K Pweter Silver/ Oyster Leather
90 300SEL 214k Pearl Black/ Alto Grey/Black Leather

Prior: 85 190E, 88 300TE, 89 300TE, 90 300E 2.6, 90 300TE, 92 300E 2.6, 91 and 93 300SL, 87 Ferrari Mondial Cabrio