Yeah... waaaaay more information needed. That's like going to a doctor and saying, "my foot hurts, what's wrong?" You gotta say, "my foot hurts when I walk on the outside of it after I sing the national anthem."
Well, I can tell you about a few common problems with the 4.0L six.
1) Check the CPS (crankshaft position sensor) connector. Get come contact cleaner, pull the connector, spray it, then put it back. If there is no CPS signal the thing won't even run. An intermittent or waek signal can produce problems.
2) Check the ignition module connector -- same as above. This is the more likely culprit! I think the coil sits on top of the ignition module (mine's an 87 model). Pull the coil and clean the contacts between the coil and module.
3) The coil is mounted on the engine in the later Jeeps. If yours is, think seriously about relocating it. The engine heat and vibration isn't good for the coil -- more than one has failed on off roader vehicles. They move it for better reliability. If the coil is starting to fail you have to replace it.
If the problem is from the start, I'd suspect the CPS or ignition module connector. If it's only when the engine is warmed up, the coil is probably going bad. But these are just guesses from previous experience. A more detailed description of when the cut-out occurs will help.