I've had the same issue. I seem to notice it most when using LTE, Spotify, and my Jabra Earbuds. I have the latest version of software on my watch. I've only had the watch 1 week and LOVE it accept for this.
My G3 overheats everytime I use LTE calls. It takes a few minutes then it gives the overheating warning. I use Galaxy Buds Live also and it seems too much for it. This needs to be addressed by Samsung. I've read several reports of this already. I have the latest update too.