1990 V8 Q Transmission Problem

[WHITEPATCH@aol.com]

After being stuck in traffic for about 45 minutes in NYC, i noticed that my
1990 V8 did not want to shift to overdrive.  I was driving up to speed (approx
60 mph) when i got on the highway in NJ when i noticed my tach at past 3k rpm.
Transmission switch is in economy mode, engine temp gauge showed about 100 deg
(about 50 deg outside) and the engine oil temp at about 60 (first line).  So,
i decided to pull over, park the car, shut off the engine then restart it.
After that, the car was fine.  Has anyone encountered this problem before?
What's the fix for it? I know the transmission is controlled by a separate
computer box; could that be the culprit?  Please help.