Dashboard Electronics sometimes don't go on

I have a 2004 with 131,000 miles on it. It has been working perfectly with general maintenance since we bought it used with 100,000 miles on it in 2008. For the holiday weekend we drove from Prescott, AZ to San Diego (aprox. 400 miles) and we turned on the car as usual and the speedometer and all the dash lights wouldn't go on. Turn Signals were fine. Tried turning off and on again and same thing. We weren't going far, so we drove it and tried to park and it wouldn't shut off. We couldn't get the key out. We drove around a little more and it shut off. When we turned it back on, everything was fine. This happened one more time but no trouble turning the car off. I also thought that it was interesting that on the touch screen/nav when the dash was "out" the consumption meter was blank. Does anyone know what is going on with my car?