Galaxy watch active2 says it needs to cool down

[Leaf6]

Just today my galaxy watch active2 (one year old) has started showing this warning on screen: power off, your watch needs to cool down.  

It then shuts down and keeps doing this even when left off for a few hours.

The things is, it doesn't even feel warm!

[Crumbz]

So I noticed that on my watch 4.. I got that notification if I had used it for a call or played a mini game on it for a while. I was a little worried it'll keep doing that too.. but I've recently had a little update and it has stopped alerting me of that, so maybe it was something they were already working on??