1999 Jeep Cherokee Wont stay on

Is the battery fully charged? If the battery is down, you need to use a battery charger, to charge it. Are the battery cables clean? Is the charging system working? Are there any troublecodes?

Some of the national brand autostores will check all this.

You may have an excessive battery drain? You can check the amp draw. If the amp draw is excessive, you can pull the fuses, one at a time, see if you can kill the circuit that is causing the problem. Sometimes it's just a lite somewhere that is staying on, inside the vehicle, in the glove box, under the hood, in the trunk. It's easier to notice a burning lite in the dark, then it is in the daylite.