Could be low on coolant or a sticky thermostat.
Either bad ground on your gauge or your electric cooling fans are going bad.
because your thermostat is opening and closing as the engine temp. fluctuates
Temperature.
A faulty temp sending unit can do that.
When you turn a corner the guage fluctuates.
Head gaskets!!
Temperature Gauge Sending Unit The sending unit is located in the front section of the intake manifold in the vicinity of the thermostat. Change it.
A short in the turn signal wiring can cause the voltage gauge to fluctuate. A loose ground wire can also cause the gauge to fluctuate.
bad temp sender usually. Bad gauge rarely.
why doesn't my rpm gauge and temp gauge, fuel gauge not work
body temp and the my mood
is the coolant disapeering at all ?