1999 Jeep Cherokee Ignition switch intermittently get's stuck or locked in the off position.

Are you saying it is locked in park ? Can you take it out of park if you unlock the ignition switch but not turn the switch to the on position ?

Hi
if you're lucky it's just pressure on the steering lock if you put your key in and shake your steering wheel side to side whilst Turning the key

Most likely is intermittent in starter solenoid relay

Next most likely is key switch start connection intermittent. a tester will have to be used to find where the power is being lost from the start terminal of ignition switch to starter solenoid pilot connection to the main starter output power from solenoid to starter main contactor.

I'm going to answer this question since I don't know how the security system would affect the lock.
If you can get the key out of the lock, you may want to spray some WD40 or other lube in the slot where the key goes.
If that does not help, you should be able to drop the cover from under the steering wheel and disconnect the switch from the lock cylinder.
If the lock is still stuck, it may have damaged tumblers or something may be jammed with the shifter and steering wheel lock.

WHEN YOU INSTALL NEW LOCK CYLINDER, TURN THE KEY TO THE LOCK POSITION. INSERT THE LOCK CYLINDER INTO THE HOUSING FAR ENOUGH TO CONTACT THE DRIVE SHAFT FORCE IT INWARD AND MOVE THE IGNITION SWITCH ACTUATOR ROD UP AND DOWN TO ALIGN THE COMPONENTS. WHEN THE COMPONENTS ALIGN, THE CYLINDER WILL MOVE INWARD AND THE SPRING LOADED RETAINER WILL SNAP INTO PLACE LOCKING THE LOCK CYLINDER IN THE HOUSING.

Buy a replacement lock cylinder at a dealer, look on www.youtube.com for a video on how to replace it. You may want to put in a new ignition switch at the same time.

sounds like the key is either worn down to where the ridges in the key wont push the tumblers inside the key lock cylinder into their proper place to move the cylinder into the starting position. Or your steering colum is locked and the wheel is moving freely as if it were not. So your solution would be to either have an expert look at it (estimated cost: 200$ low/400$high) or you can attempt to fix it yourself.
should you choose the "I'll fix it myself" method....try getting a new key made at a hardware store since keys wearout over time (ie:10years of turning that old key), this may solve the problem right away if the ridges are just worn on the key. Or the hard way, you need to get a phillips screwdriver and some jewelers tools and an 8mm or 10mm wrench/rachet+socket to disconnect the battery, then underneath the steering colum just under the ignition is a hole in the colum shroud/cover, from there you can disconnect the ignition key lock cylinder (the thing you put your key into). once you've removed the cylinder from the steering colum you should test your key again to see if you can turn the cylinder outside of the colum if you cannot then buy a new ignition key lock cylinder for about 15$-30$...problems solved.

ignition got stuck you need to check the inside of it probably replace it thanks

If this is an after market alarm, the alarm is in the off position.
Look under the dash on the drivers side for a push button or switch.
Turn the key to the run position without starting the car, either push the button or move the switch in the opposite direction and turn the key off.
This should turn the alarm back on.