as a mechanic myself, i'd venture to say it could be a couple of things, IAC/TPS is most likely, if you've replaced those check your fuel filter (not sure if it's serviceable, mine is not), i've seen cars that crank and run fine until they get warm, die, and you can't crank them for an hour or so just due to the fuel filter putting too much strain on the fuel pump. If that doesn't do it, I may be able to help you if you can provide a little more info (what have you replaced recently, et al)
Current: 1998 Cherokee Classic (White)
stock with 263k miles yay!
SOLD 1999 Cherokee Sport (Black)
~6" Franken-lift (2" CSS/ Rusty's 180lb 3" front springs, S10 bastard pack w/ 3" Rusty's AAL)