Iphone 12 heating up

iPhone heating up too much , while using. And its happening on left side buttons.

some observations

1. While charging and phone is on.
2. While using on Charging an on.
3. Left side buttons and around the lens while on.
4. logo lite will flicker down while restarting/screen brightness also decrease automatically.

I have seen few posts about heating up... is it mainly due to due to 5G network is set to always on and automatic mode. ???