thermometer icon on apple watch

So I'm working at my desk, my office is at 70 degrees, my Apple Watch Series 5 (that I bought 4+1/2 months ago) is sitting on its (Apple) charger, not near any direct heat/cold sources. I go to pick it up and put on, and it's got a thermometer on the face of it and has shut down. As soon as I pick it up, it reboots and everything seems to be fine. The watch doesn't feel hot or cold, the charger doesn't feel hot or cold, my office isn't hot or cold, so what the heck is going on? It hasn't been exposed to any extreme temperatures. Heck, I don't even wear it every day! Have I got a "lemon"? It's not even 6 months old yet!