2000 Plymouth Voyager instrument cluster blinks on and off

The instrument cluster blinks on and off at times and other times remains burning steady. It has speedometer, gas gauge, temperture gage. Some days they work fine and other times I turn the key on and the lites won't come on or they blink on and off. The headlites work, as do all the other lites. This only affects the dash lites, not the radio, either. Do you know why this is happening? Please reply.
Sincerely,
Grier Robinson