Bad temperature gauge or sensor?

[Meanwhile]

One of the gauges I pay a lot of attention to is the temp gauge. About a week ago I heard my fan come on, I looked at the gauge and it read about 185 degrees. It struck me as odd so I started paying more attention to when the fan come on. Now the fan comes on more frequently when the gauge is around 180-185 degrees but it also comes on between 200-205 like usual. My first thoughts are pointing me to something gauge related. Have any of you experienced anything similar?

Another odd thing about this truck, I could’ve swore it idled at 650 rpms but now it’s idles at 700.