Thats the same problem I had with my old 98 SE. If you smack the dash they would come back on
What you need to do is remove the gauge cluster and clean the pins where the wires meet the cluster. I cleaned the pins with contact cleaner and the put electrical grease in it and re-assembled. Only took a hour or so and I never had the problem again.
Its an easy fix if you just a little mech. inclined.