MB8, 90hp, engine goes off spontaneously

Hello, the engine goes off spontaneously. During the ride or in the stand. No matter whether cold or warm driving. No matter whether dry or humid weather. Sometimes on a few KMs often in a row, sometimes hundreds of KM no problems. When it is off, it can sometimes be started immediately again, sometimes it requires several attempts. Finally, it was possible to determine slight regularities: twice in a row, it went out directly when inserting the reverse gear (return light?). A few times directly when pressing the turn signal on the right. Once when turning on the windscreen wiper. This all within a few KM. After that, the whole thing could not be reproduced again. A few weeks ago, the ignition coil was re-engineered on suspicion and the throttle flap was cleaned. This did not help. The battery is top. At the moment, the car is back in the workshop.