Gauge Jump to Max at Start up - 99Z28

OK...have not been here in a while...car has been doing great. Car just started doing this during the last 3 weeks. Does do it every time..seems to be random. Car has original alternator with 120K miles. Battery is about 1 year old... Interstate 72month....
Any have this before...fix ???
Thanks, JJ

Let me clarify...All the gauges Jump to Max and then return to normal. It also resets my trip odometer. Car start fine !!!