I have replaced the battery 3 times over the last 2 years, replaced the alternator,belt, tuned-up performed, had the car checked by a Cadillac dealer who checked out the ignition and electrical system and found no problem, but the when I drive the car for over 20 minutes, shut off the motor and try to restart, I the engine does not turnover. Just silence. If I wait about 15-20 minutes and attempt to start, the Fleet will start up about 80% of the time.. :hmm:

I have to keep a jump booster in my trunck to get it to start, even that sometimes does not work.

Can anybody tell what is causing this. Otherwise, I am a diehard Caddy man.

I would guess that your problem is that the cables going from the battery to the starter and the ground is screwed up. Have those checked and changed if necessary.

I heartily second AElayyat's advice. Past that, I would think about a draw test on the starter. (Old age x mileage) + heat soak = crotchety starter.