Yes Oldchestnut this has been a common problem with many S21 Ultras especially when they were new. My 512 Gb Exynos S21 Ultra used to get way too warm when just opening the camera app. I didn't panic and just gave the phone time to bed in and sort itself out and it settled nicely by just using the camera a little at a time at first to the point I am at now when I can record lengthy videos and take lots of pictures all in the same photo session during which it only gets pleasantly warm with no overheating shut off in sight. Some people are not so lucky however and if you are finding that your phone is not settling down (mine took about a month) and is overheating to switch off too often then I would genuinely consider taking it back and getting a replacement. You are paying a lot of money for what should be a phone that is a joy to own as mine is now and not be constantly worried about it overheating all the time Oldchestnut. Hope you end up with a cool running phone as soon as possible. 👍👍