Temperature gauge reading/thermostat

I started the truck this morning it sat over night. The temperature gauge in the truck read 210 within 5 minutes. On the way to work the gauge read up to I think 240 then dropped back down to 210. When I left work the gauge read 210 and the temperature went up to 240. The thick line between 210 and the red line being 260.

My question, is there a sensor or what my guess is that the thermostat needs to be replaced?

The gauge shows it runs between 210 and I think 240 it has got between the 240 mark and the red 260 but only while sitting idling. To answer your question about running hot or overheating, it doesn't seem to be over heating. No water being pushed out onto the ground that I have noticed. The temperature gauge on the dash was replaced about 6 months ago. Now it has always ran at the 210 since I have owned it.

If it is a sensor would that show on a personal INNOVA CarScan Pro 5210 Code Scanner? I do have one. Also I bought the truck used in 2017 no records of previous maintenance. If it was a sensor would that effect the temperature gauge?

Your wisdom would be very much appreciated for this shade tree mechanic. Thank you very much for your time you all are so very awesome.