I have a 1989 740 turbo wagon, and it has some trouble starting up in the morning (just like it's dad). Generally I have to crank it over for a while before it does start, and when it does, it will rev up and down (between the fast idle speed and 200 RPM) In my honda, this problem would be very similar to air bubbles in the coolant system. Many times when the engine speed drops, the car will stall. It starts right back up, and it only stalls when the car is cold. After warming up, the car generally idles roughly. Now, this may be a combination of problems, but I have checked the distributor, and replaced the plugs and plug wires. I'm not sure if this car has an IAC valve, and thus am not sure if that could be a problem. Any help in the matter would be most welcome.

Clean the throttle body good and the idle motor.The idle motor is located under the intake.

If your problem still exist, try replace a new distributor rotor & cap.
That solved my identical problem with my 760GLE.
If you still have momentarily stall problem, replace the ignition control unit.
I replaced mine with a replacement part from junk yard & problem solved.

Good Luck! :)