I took my Gear Fit off and put it on my nightstand while I took a shower, when I came back out it was in a constant reboot. I know it was charged since I had done that last night.
I tried everything I could think of, holding the power button didn't seem to do anything. What finally got it out of the reboot was hooking it up to the charger and holding the power button until I felt it vibrate twice. I had tried that earlier, but only felt one vibration and let go of the power button. So if anyone experiences this behavior, hold the power button until you feel two vibrations and hopefully yours will come back up as well.
I did have to pair it with my phone again, but all my settings were still in Fit Manager. Only had to switch screen rotation and wallpaper.