Coolant temp. needle acting funny, some more idling issues

[arcter]

Hey guys. My car for the most part has been fine recently, but I have noticed that the coolant temp gauge is all over the place. I mean, it actually stays pretty much in the same vicinity but it does a lot of twitching. It never just stays still. And when I first start the car up for a minute or so I sometimes get REALLY low idling, like it's going to stall, and it stays there so I have to give it gas. Clears up after driving for a few minutes. Are the two issues related? Do I maybe just need to bleed the air from the coolant?

[Choking Hazard]

Two things or more going on-  coolant guage gets weird b/c the ground on the back of the instrument cluster gets loose.  Car overheats pretty quickly if something goes bad, like a thermostat, which (for me) had to occur while I was disregarding the erratic temp readings.   Then the cylinder head cracked at its know weak spot on cyl #2, and I got a really bad start stumble and then it would blow out/ dry up the coolant with the exploding air/ gas mix.  I know that is more than bad news, and could be totally not applicable.  see if the #2 spark plug is wet.  Try to smell for coolant in the exhaust.  If these are negative, at least it probably isn't a major internal problem...