Engine Performance problem
1997 Jeep Laredo 6 cyl Automatic 172000 miles

The engine in my jeep will stall out and after a few seconds will then kick back in and continue on. It is only doing this in the mornings. So far, we have replaced both coils, the crank shaft sensor and fuel filter. Most of the time, the engine light does not come on, only after it completely shuts down and dies does it come on. Friday, it stalled out 3 times but the light did not come on until that afternoon when the jeep was running fine. I had it tested again and this time is said "low catalylist". What could be causing this problem? I have had it in 3 different shops so far.