Expounding on my last post, sometimes my water temp gauge will be happily sitting at 180 as I cruise down the boulevard.
Suddenly it zooms up past 260 and pegs. It takes about 2 or 3 seconds to climb up like that and then comes down almost as quickly, right back to the 180 area.
Gauge problem or is there some sort of superheat problem happening?

If its a gauge problem, what would I check? Its a nice liquid filled hood mounted gauge but it is somewhat old.

That sounds like an electrical problem with the gauge or temp sending unit. The gauge may be grounding out and just pegging. Make sure all of the wiring between the sending unit and the gauge is in good condition. If it is, then I would replace the sending unit.

This could be a stuck t-stat that all of a sudden pops open and once the system is flowing cools down. Check your guage and sending unit too though as suggested. My old El Camino use to do this every day when I just started driving it. It climbed way up them dropped real fast once and then was fine the rest of the day. Let it sit over night and it started all over again in the morning...