Q: Mercedes 380SL starting up, rough idling, then cutting off and dying

The mileage is not that high but due to the age, before attempting further diagnostics, you should test cylinder compression and intake vacuum (to check for stuck valves). If you determine that the engine is basically mechanically sound, there are lots of possibilities, one of which is plugged fuel injectors, again due to vehicle age. If the fuel injectors on this vehicle have not been recently cleaned, they should all be removed from the fuel rail and sent to a lab such as Mr. Injector for service. Typically these injectors have a miniature filter basket that is replaceable. Cleaning injectors on a car is a waste of time and money and the injector itself has to be cleaned ultrasonically in a cleaning fluid and, as noted, the filters must be replaced. In addition, they must be flow tested. Prior to removing the injectors, it is possible to use an oscilloscope to look at secondary firing patterns to distinguish between fuel versus ignition trouble. If you desire that this problem be diagnosed by a certified Mechanic, dispatched by YourMechanic right to your location, the recommended service is a rough idle diagnostic. If you request that service, the responding certified mechanic will get this resolved for you. If you have further questions or concerns, do not hesitate to re-contact YourMechanic as we are always here to help you.