It is normal that the temperature of the watch will be a little higher than usual when charging, because it is the conversion of this part of electric energy into heat.
If your watch is overheat during charging, please check the following steps:
a. Check if it is connected securely to the charging base. If not, press or adjust to make them connected tightly.
b. Check if the USB port, charging adapter, outlets or the charger is faulty. We recommend you charge it with your PC or phone charger (Rated input voltage: DC 5.0V ; Input current: 500mA).
If the watch is still overheat after factory reset, you can contact seller for help.