Samsung M 21 2021 Edition Over Heating warning Error with in 20 Seconds app will close Automatically

I am using Samsung M 21 2021 Edition model from starting launch September 2021 onwards with Exynous 9611 processor. My usage is very basic like phone call , Video call , SMS & Basic payment app with Online/ Offline video watch along with YouTube or facebook app nothing else .

Never updated phone due to scare with any time green line issue or phone mother board damage or dead after any updates.It runs very smooth without issue.

from last two days i am facing overheated displays warning message that app will be closed automatically in 20 seconds.

Don't know what trigger my current location is bengaluru temperature is not bearable in night too here weather temperature keeping around max 38 to night 30 deg. c approx .Never used phone along with charger always avoid.

I am facing some other issue as well like below -

1. Samsung overheated displays warning message that app will be closed automatically in 20 seconds. I tried facebook , youtube & Whatsapp Video call all 3 app process i found same issue there is no unnecessary back ground app i can see or installed in phone.

2. If we change Data sim n/w from sim 1 to 2 or reverse some website not able to access seems something restricting if restart again phone it works fine seems this cycle repeat every time if change sim n/w no issue with wifi connections. Here like paytm, other payment apps some chrome browser website not able to access.

Kindy Samsung users please help me above issues to overcome if anyone faced recently or other smartphone brands have similar issue.

What things need to avoid i am not looking to change phone further atleast next year it is Samsung M21 2021 Edition 4/64GB Variant.