Had some work done to the car recently. Put in new gaskets, intake, exhaust, new wires, opti. I noticed now that the temperature gauge bounes up and down. It will be working fine and then it will just go all the way down as if the engine was cold. 3 minutes later it will go back up to the correct reading. Is something loose?

 

Probably melting the wire/pigtail with your headers. The the sensor installs on the drivers side. Here is a picture courtesy of the wonderful shoebox http://shbox.com/1/temp_sensor2.jpg I did this twice. I ended up having to use some high temp marine heat shrink tubing then covered it with that reflective aluminum heat tape.

But check that area out for a melted wire or maybe the pig tail is just damaged or loose.