If you leave your key in the ON position for about a minute or so, will the gauges then begin registering? Or, leave your key in for 30 seconds to a minute, turn it off, and then back to ON. Do the gauges begin working? Don't try and start the Jeep during this test. Just see if your gauges come to life.
I had that problem for ages. The gauges would take a while to "come to life", especially in the winter. I could hear the clicking of the fuel pump and ASD relays in the engine bay and then the gauges would register. Once they would register, my Jeep started right up.