You can try these steps, your phone won't be wiped. Enter settings, then type reset into the bar. Do reset settings, accessibility, and network. Reboot afterwards.
Also, are you using a wireless charger without a fan? It produces more heat than wired.
Hi,
this last Monday (4/29) I woke up and my Galaxy S10+ was extremely hot, right under the Bixby button and on the back in the same area. I haven't charged it overninght because it was charged the evening before. The one thing I noticed is my Watch Active died overnight (i thought it will last till the morning). I checked and there were no apps draining the battery, yet the phone was really hot. After I restarted the S10+ it cooled down and is still ok. At the time of restart I put my Watch Active on the charger (letting you know in case it matters, it was charging however it didn't power on). Today I noticed that the left side of the phone (that was hot) seems to be swollen a little compared to the right side that remained cool. Please see the attached photos. Hope it's not the Note 7 disaster all over again (this time without even charging). Anyway, this phone is not in its original state (pretty much the body is 
