Wild Coolant Temp Fluctuations

Hey, all.

I was sitting at a light and the temperature needle was at it's usual hash mark before the 220 reading. Out of no where the needle jumped to 280 faster than I could blink and I received the engine overheating chime. Then in the same speed it went back to the hash mark before the 220 reading. Then it went back to 280, and in small fast incrents went back down. It repeated this cycle until I began driving and stayed at normal operating temperature.

The coolant system has not had any maintenance performed on it recently. The fans kick on. Coolant is at the appropriate levels. For that reason I don't believe air is trapped or there is an issue with the fan relay or fans.

Any thoughts? I wanted to drive and replicate it to see if the Aerogauge reads differently, but if I recall it's the same signal.

Bad sensor? Bad ground? Are there any purge lines that could be clogged?

Car has 60K miles and is a 2013 MY.

Appreciate any insight.i was going on a road trip tomorrow but that may not happen now