1999 Jeep Cherokee RPM Drop to Zero &/or Car Stalling W

I have read through the forum a few times, but didn't find anyone with my exact description.

I recently had my car inspected and it passed, but I had told the mechanic about my car stalling while driving &/or stopped. He ran my car and couldn't find anything that would cause it, nor had the problem that day.

Here is what has happened the past 2 days; I will drive the car for about 15-30 minutes and the car will drop to 0 RPMS while I am still driving. The car will coast for about 2-15 seconds and then it will catch and the RPMs will go back up to normal (around 2.5) or if it coasts for too long the car may just stall. Plus sometimes when I come to a stop light the car may just stall. Whether the car stalls while driving or at a light sometimes it will start back up no problem, other times it takes a few cranks or giving it 5-10 seconds to sit to restart.

I am trying to figure out what this could be. What would you suggest?