Not too many suggestions to help you out here, so here's my 2 cents.
Too me, sounds like a possible ignition module. Fords were notorious for this symptem. And I believe a lot of Jeeps used the Ford ignition system. A way to check it out is, next time it dies, pour some cold water over the module. If it fires up right away, that's likely your problem. Or, you can have the module checked out at some auto parts stores, except they usually tend to say they are no good, just to sell a new one.