Could be almost anything. A bit more diagnosis will be in order. My first guess is it is getting flooded, fuel from leaking down injectors will foul the engine up when sitting.

A question, hot starts or cold starts, any difference?

I had similar problems with mine but just replaced almost everything, injectors, plugs and wires and guess I got lucky and the problem went away. You will need to do a bit more work on your own and then come on back and ask a few more questions.

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Chas

Had a 380SL, 450SL, 380SEL, 420SEL, 500SEL

Got a Euro 500SEC right now.