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Assistance required for R129 SL500 halting problem

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Hello, everyone.

I own a 1997 R129 SL500 and it is experiencing a problem.

The occurrence started last week. While travelling at a speed of around 5 mph in traffic, the vehicle had a sudden and brief decrease followed by a rapid increase in engine revolutions. Subsequently, all dashboard lights illuminated and the engine stopped. I had no difficulty restarting the vehicle and thereafter drove one mile back home. A few days later, I drove a short distance without any issues, then it stuck at traffic lights shortly after. No fuel problems, no spluttering or misfiring, simply sudden illumination of dashboard lights and engine shutdown.

I brought it to my independent Mercedes specialist who connected it to Star diagnostic system and found no issues. He said that it may be a crank position sensor, so he purchased one. I drove to his garage without any problems, but it stuck again when I stopped at adjacent traffic signals. He installed the sensor and hoped for the best, but unfortunately, the engine began briefly and then stopped again. I drove a little distance home and the vehicle stalled once while stopped, but restarted without any issues and I was able to drive back. I waited for a few minutes with the engine running outside the home. Suddenly, there was a brief reduction in revolutions per minute, causing the engine to stall in the momentarily before restarting without any problems. I'm curious whether it occurs more often when the engine is heated.

The car will get a check-up by a traditional Mercedes expert on Monday, which is annoying. I intended to drive 25 miles today, which may be OK, but I am concerned about the possibility of stalling at high speed on a dual road.

Has anybody encountered this and can provide any recommendations?

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I had a problem where the engine would start but then promptly shut off. Initially suspected the crank sensor, replaced it, but did not see any improvement. Battery replaced successfully. I believe that the decrease in voltage after the start-up led to the ECU experiencing a brown-out and resetting.
It is possible that the battery is experiencing sporadic internal contact issues or is beginning to deteriorate.

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