Radio/GPS Unit Display & Controls Dead (for a while)

Developed a problem with our GPS/Radio in our 2003 GC. Occasionally,
the radio/gps display and buttons will not work. The problem
"sometimes" occurs when the vehicle is started (radio/display works)
and then shut off and restarted. The radio will play the last tuned
station but none of the front panel buttons function nor does the gps
display light up. Turning off the Jeep, leaving it for about 5 minutes
and restarting corrects the problem.

Also noted, when the problem occurs and the vehicle can't be stopped
and restarted the radio/gps display & buttons began to function after
about 40 minutes.

Any ideas?

Thanks

KP