Wiscoburban

2016 Suburban, 5.3 L, 54K miles Ride home yesterday presented an issue I had never encountered. The temp gauge is usually pegged at 210 all the time. yesterday towards the end of a 250 miles road trip, the gauge starting going down a few widths of the needle and then back up to 210 for a bit, then back down...it has been doing this now since yesterday. I bought and installed a new temp sensor, thinking it was just a sensor issue. It continues to do this. Never goes above 210....yet. It is producing heat...when the heat was on full heat and full fan, the temp did drop lower than the previous...but then again went back up to 210. I am not sure what to conclude next or why it maybe happening..looking for some opinions... Thanks for your time.