I have my Galaxy S22 Plus is always too warm whilist using, even when I reset the device and removed the case cover. The device is only 4 to 5 months old. No app running in the background as I just reset it.
This is a known issue and I have the same problem. Intermittently the back side of the phone heats up. I didn't find any solution since more than a year. Let's see what the upcoming S23 ultra behaves.
Just because you have just reset it, doesn't mean that some background apps haven't restarted. Do a bit of Googling on that. Turn off automatic updating as a test to see if that is affecting it. Reset your network connection to 4G, again as a test. If your 5G coverage is borderline your phone may be switching from 4G to 5G and back frequently, working harder to do this. In any case for most of what you do, unless gaming, 4G will do the job. 5G is .often even slower than 4G because of distance, greater need for line of sight, etc. I wish I could remember the link I had on this, sorry. If you want to check coverage, load an app called Aus Phone Towers which allows you to check coverage for 4G vs 5G, etc., different ISPs, and many other factors. When using do you have the charger connecred, because even that adds load. Google has heaps of more info so Google S22 overheating.
