My Samsung watch randomly turns off and the battery is not low. Sometimes you can turn it back on and other times you have to either place it on the charger until it lights up and then you can turn it on or hold the power button for 10 seconds.
Thank you for reaching out! Please send a private message with the model code and the serial number or IMEI number of the watch, and troubleshooting steps you may have tried. http://bit.ly/2XERsky