Thank you for reaching out. I'm sorry to hear about the symptoms you are experiencing and would be happy to assist you further. Can I please have your full model number, serial number/IMEI, and any pictures of the symptom you are experiencing in a private message: http://bit.ly/2JH2rq2
My wifes watch (same exact model as yours) did the same thing last night (7-5-2020), the sensor became so hot it burned my wifes wrist and the glue that holds the sensor glass melted so it is no longer attached to the watch. I also filed a report with Consumer Product Safety Commission CPSC.gov, everyone who is having an overheating problem needs to file a report. It is important to do this because of the danger, one: is the loss of use of the watch, second: is the potential for an injury, third: if this device catches fire while on the charger it can cause a house fire placing everyone at risk in the home.
I suggesting this because of safety, I was an inspector for the US Army in the feild of electronic's with over 20 years of experiance in the field. I trained soldiers and inspected their work daily on much more sophisticated equipment and reported systemic failures by product for suggested improvements. The Galaxy Watch is a danger (you & my wife burned) not to mention the larger implications of harms that could come from this overheating issue.