I've had the exact same experience on MB's and had 3 different issues.

1. Defective Battery, most common. I couldn't even jump start. Replaced battery, no more problems.

2. Defective Neutral Safety Switch. Started the car with a push button start switch. Replaced NSS, no more problems.

3. Defective Starter. It started out intermittent, passed bench test at one auto parts store, then failed at another. Replaced starter, no more problems.

Check all the basics first.

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1993 190E 2.3
2001 SLK230
1971 LS5 (454) Corvette Convertible