I have a 1987 E230 that very intermittently cuts out or seems to while driving at any speed. If you stop and restart the engine it seems to work fine again.

it may be anything from a vacuum leak to a throttle positioning sensor, idle speed solenoid. Have it scanned & get the live readings.

Engine stall or RPM fluctuates at idle.

This problem is commonly caused by a dirty automatic idle speed control valve and throttle valve. Buy a can of throttle valve cleaner (do not use carburetor spray cleaner!) from NAPA or Carquest (made by CRC chemicals) and spray it into the air intake while the engine is running, use up about 1/2 the can, engine will try to stall hold the speed up, shut it down and let it soak for 30 minutes, restart and blow out the remaining fluid, shut it down and disconnect the negative battery cable for 5 Min's to reset the base idle control

Electrical probblems are always the hardest to solve. I don't believe it to be the ecu, because when one fries it doesn't work at all but that may be the case. I believe from what you describe there is a short somewhere between an important censor and the ecu, like mas, 02 or throttle positioning censors. Ive also come across cases of which the catalytic converter was clogged making the car not operate correctly. Hope this helps.

Here is the common cause of surges, stalls at stops, slow idle speed, erratic idle speed, rough idle and engine hesitation (and other problems), it is in most cases the idle speed control air-bypass valve and or throttle valve and upper intake, these area's get full of gunk and combustion residue over the miles and cause idle issues (stalls, low idle) like yours, Get a can of intake cleaner from any local parts store, not carb spray, intake cleaner, it is made by a company called CRC, remove the air intake hose to the engine, hold the idle high so the engine won't stall, then spray the can of cleaner into the intake while keeping the engine running, use at least 1/2 the can, shut down the engine and disconnect the battery for 5 minutes, then restart and complete a number of mixed driving cycles, town, freeway, stop and go etc., after a few days the problem will go away as the system will relearn to the clean intake.

try removing battery and cleaning all the ground under the battery tray and check main ground wire from battery to engine

Ignition system. For failures that cut out like this is a common sign of a ignition system failure

Your problem sounds as if the thermo sensor....which controls the air fuel ratio when engine is cold....is faulty. It is a common fault on this model.
This is not an expensive part, and takes only a short time to fit.
Good luck
John

sounds like the idle speed sensor,if your rpm's are idling up and down

If its the 3.0 diesel it could be the rail oil pressure sensor starting to pack up .

I had a similar problem once. I would take it to AutoZone or Advance Auto Parts and get them to scan it for codes, they will usually do it for free. It could be the speed sensor, at least that was the problem for me. Hope this helps.