Sticking Tempeature Gauge

[pberku]

The needle of my temperature gauge occasionally sticks at 0C when I start the car and will not move up from that position as the coolant heats-up. Occasionally it will suddenly jump to the proper temperature. When stuck, if I tap on the instrument cluster lightly it will unstick and jump-up to indicate the proper coolant temperature. Once its un-stuck from the 0C position it will work properly until the next time I turn the engine OFF and ON again.

Has anybody ever opened-up one of those gauges? What's inside that could make it stick? Is there something I can do to fix it? I never touched this thing.

Thanks