I just purchased a Galaxy Watch 4 and am very disappointed in it. Today alone I have had the watch on for 4 hours and it has gone into cool down mode 3 times. I have gone back to Telus (where I purchased the watch) 3 times over this issue and the battery not lasting 12 hours. The first "fix" was changing the power block the charger was plugged into. Apparently if you do not use the correct Samsung block it will not do a full charge even if the watch says 100%. Second "fix" was to put my watch into power saving mode and turn off all the notifications. This "fix" did nothing for the overheating or battery life. The third "fix" was well we do not know what is going on we have had no other issues. I am frustrated that I am paying for a watch that I can not wear more then 6 hours. This issue seems to be common with this watch. Does any one have any tricks or tips to help??
I am sorry to hear of your Watch constantly overheating and the poor battery life, and can see how annoying and frustrating it is. Whether you're using a phone, tablet, smart watch, or earbuds, all Galaxy devices have a set temperature range, where they operate at their best. While they may feel warm under certain conditions, like charging, this does not affect the device's lifespan or performance. However, if your devices get too warm, it could cause some issues. Use this guide to help keep your devices at their normal operating temperature. Try this guide: https://www.samsung.com/us/support/answer/ANS00076952/
Also, you can improve battery life on your Watch with this guide: https://www.samsung.com/us/support/troubleshooting/TSG01003232/
Please let me know if this helps.