trouble starting

My 1992 cherokee is having trouble starting. Sometimes when i try to start it it seems to lack power and it eventually starts. After driving it for a while when i turn it off and try to start it again it seems perfectly fine, but if it sits for a couple of hours the problem starts all over again. I dont really know anything about cars at all, but i was thinking the battery might be old. If someone can give me some idea what the problem is i would really appreciate it.

I have the same prob w/ my 98 jeep, what I cant figure out is its only in that certain time period it seems to act up. If its sits longer or shorter its fine, but the 1 and 1/2 hr mark it always seems to mess up. Acts like it fires on about 3 cyl, usually dies and I have to crank 2nd time then it fires right up. If you found the problem let me know, I'd appreciate it too.

Thanks,

Jeff

Forgot to mention, it MAY be related to the battery...it seems to not do it as much or as bad if I throw the charger on my batt, but I have a new batt, I'm thinking it may be the alternator cuz after a week or so it seems to come back. But I dunno, if it were weak batt I'd think it'd crank sluggishly all the time, but it doesnt. I think its just coincidence it seems to get a lil better after charging w/ an external charger.

are there any codes stored in the computer? Try this link to learn how to retrieve the codes and then let me know more.
http://minimopar.knizefamily.net/fault/index.html

Ok, i also forgot to mention that when the car is almost dead and really doesnt want to start the check engine light started to come on and after driving it awhile when i turned the engine off and started it again the check engine light would turn off. so i took my jeep to the mechanic and he told me it was my alternator, which basically started to kill my battery and it really couldnt hold much of a charge anymore so i needed a new alternator and battery.
-- Thanks to the people who replied to my problem!!