iphone 7 heating after 5 minutes.

That's a very OLD iPhone at this point. If the battery hasn't ever been replaced, it was likely due for battery replacement long ago. But honestly, since iPhone 7 is considered Obsolete by Apple, it wouldn't be worth even spending the money to replace the battery.

To check your Battery Health, open Settings > Battery > Battery Health - if as I suspect, it is at 80% or lower, the useful life of the battery has been used. It's honestly time to buy a new iPhone at this point. iPhone 7 was released in 2016, 9 years ago.

Given the age of that device, the battery is probably failing.

Check the battery health. If it's at 80% or below it needs to be replaced.