Car runs for about 20 minutes then shuts off. Has to cool before it starts

What is your question?

No unpredictability. Just stops. Will crank but no start. Doesn't matter if gas tank full or empty. Taken to 2 different mechanics, didn't do it for them. Changed the computer sensor module, coil packs, and c am sensor.

How long has your 1994 Buick LeSabre had this problem?

Off and on 2 years