I drive a 1999 Buick Century, and the dash board randomly cuts out. no speeometer, no fuel, no engine temp, and all the warning lights flick on and off and go dead. the doometer display and gearshift indicator (digital, found on dash) also go out, but the odometer still keeps accurate track of mileage. does anyone have any idea what to do? or had a similar problem?

we already checked grounds on the car so we know its not that, and i had it in once to the dealer and they said it checked out. things are to the point where i dont need the gauges (i can gauge 25- 75 by eye within a few MpH and i know my cars gas mileage... only issue is temperature) but to re-sell the car, i kinda need them in working condition, so any help is appreciated