What I recommend is to monitor your coolant level and keep rolling (local drives only). If the fluctuations continue, take it to your mechanic or start going down the list yourself. If the temp goes hot and doesn't return to normal, stop and let the engine cool down before trying to drive it any further. (A tow truck ride to your mechanic is far cheaper than having your engine overheat.) Still recommend everyone own an OBD II scanner. I would plug that in to check for any codes and to see if the sensor signal matches the gauge reading. If you're doing it yourself, recommend NOT buying "OEM" replacements from EBay or Amazon due to the high number of counterfeit parts.