About 3 weeks ago, my 99 tj started to occasionally die as I was driving. Usually, after a minute or two it would just start back up. Then it died on my way to work one afternoon, and wouldn't start back up. I did some checking, and it turned out to be the crankshaft sensor. It was an inexpensive and easy fix, and has since been working perfectly. I'm not sure if that is the problem you are having, but it could be something to check.