Temp. gauge bouncing up and down

try the thermostat first its cheapest 195*

It sounds like air is in your cooling system.

You can burp the system. While the coolant is cool, remove the radiator cap and start the engine. Allow the car to warm up and you should see bubbles and hear the system burping. If that's your problem you can expect to have a little overflow while it burps, don't worry as this is normal. Just get a couple of rags and put it around the radiator neck.

It can also help if you gently squeeze the upper radiator hose to help facilitate the release of air.

When everything is good to go you should be able to see the coolant running through the radiator and have no more bubbles coming out.

If you're interested in changing/flushing your coolant you can, especially if its a bit aged, but it certainly isn't necessary.

Maybe a bigger question for me is that if it's air in the system, how did it get there? Did you do something recently, change hoses, etc?