My sense 2 reboots within seconds of starting any activity on the watch. I doesn't matter which activity. So far I have tried forgetting the device in Bluetooth settings and repairing , uninstalled all but one official Fitbit watch face, factory reset 3 times, force stopping the Fitbit phone app, clearing app cache and clearing app data and repairing thru the app. But none of this works to fix the issue. I am very disappointed in Fitbit and Google for such a disaster of a watch.
