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Q: Why does my olds 98 stall sometimes and then immediately restart? on 1990 Oldsmobile 98

The condition occurs most often after idling for a few minutes such as in traffic or waiting at a store. Sometimes just driving it will stall or start running rough. Without exception turning the key off and immediately restarting it clears the problem. There have not been any codes set and have not been able to duplicate when connected to a diagnostic computer. Any ideas?
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One of the most common cases for intermittent stalling on your 1990 Oldsmobile would be the crankshaft position sensor. Another likely cause would be the mass airflow sensor.
To add to Jim, the coil packs and module assembly on these units overheat and fail very often, particularly when they get hot. get it checked from a shop with a bid.

Mastertech is also correct. I left those two items off of my list because ofter when they fail the car will not restart immediately as seems to be the case here.
The crank position sensor and ignition module have been changed. Are there any tests that might narrow down the problem? I've had the car to a local shop where it was connected to a diagnostic computer. There were no set codes and no issues. The ECM and mass airflow both passed the usual 'tap tests'. I'm rather frustrated with it. It runs perfect most of the time, including when the mechanic examined it; the it will just stall or miss badly. I don't understand why cycling the key and re-starting with no wait time clears the problem...
Even though the ECM passes the "tap" test it could still be failing intermittently. Cycling the ignition off and back on again allows the computer to "reboot". There is really no better test than to replace the ECM and see what happens. If there is wiring or connector issue simply cycling the ignition off and back on would not commonly cause the problem to correct itself.
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