I had similar problems with my 82 380SL cutting out as you describe at any time without warning including highway speeds then not restarting for minutes to hours. I followed the usual suspect repair list of OVP, Fuel Pump relay, fuel pump operation and connections, rotor distributor cap, under hood wiring connections as you have. The engine would crank easily, and the fuel pump was operating, but no spark. I replaced the ignition control module and the problem stopped. I do not know if your car has the same ignition module system. Good luck, this kind of problem is very frustrating.

I hope this helped
JRJ

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82 380SL euro (sold)
93 400E (sold)
99 BMW 328IC (Wife)
2001 GMC Yukon XL
2001 Honda Accord (son #1)
2005 Mazda 6 (son #2)
2006 Honda civic (daughter)
"Always too many cars in the driveway"