Is it normal for the M600 to feel hot when wearing/charging it?
The M600 works best when the internal temperature of the device stays between -10 degrees and +50 degrees Celsius (14 degrees and 122 degrees Fahrenheit). The M600 will regulate its internal temperature if necessary, but if your M600 is heating above normal temperatures when you're wearing the device, remove the M600 from your wrist and turn it off. Or, if you're charging the M600, remove it from the charger. Leave the M600 to a cooler place to cool down before wearing it again or continuing to charge it.
Also, take care not to leave the M600 sitting in direct sunlight for a prolonged period of time, or in to a car on hot days, or outside in temperatures below zero degrees Celsius (32 degrees Fahrenheit). You should also avoid exposing the watch to dramatic changes in temperature or humidity. Storing or using the M600 in temperatures below or above the recommended range could shorten the watch's battery life or cause other damage.