Occasionally my 1999 Cadillac Deville'* windows, radio, truck release, gas cap release quit working all at once but after time they all begin working again. I've been looking around the internet for a fix and I think it is the Rear Integration Module? Don't know where it'* located or if that'* the problem.
I also have a dashboard that is not displaying correctly, it'* just a bunch of unrecognizable characters.
It is a low mileage 1999 Cadillac, 97,000 miles.
Your assistance on these issues would be greatly appreciated.

Best Regards,
Electron

You checked the alternator?

Sometimes electrical gremlins are a result of a failing battery or alternator. Running a couple of volts below the norm can cause all sorts of problems. Check the battery and charging system to make sure everything is working as it should.

Agree totally. Maybe even just disconnect battery terminals, make sure they're clean, then reconnect them. I had to learn that lesson the hard way a couple of times on my LeSabre. Slightly loose terminal had me chasing all kinds of body gremlins while the car ran fine.