iPhone 14 Overheating

The phone is designed to let heat from use, especially intensive apps and processes, escape thru the case. See If your iPhone or iPad gets too hot or too cold

Since the phones only a couple days old, it’s still likely calibrating Leave it a few more days to finish its housekeeping (calibration). Leave it on charge, on Wi-Fi, all night every night so it does the housekeeping overnight. 

This user tip contains a number of ideas, too.

The last update killed my battery! - Apple Community 

iPhones have built-in temperature sensors, and if the phone’s temperature goes outside of safe limits the phone will shut down and display a message saying it has to cool off (or warm up). If this doesn’t happen it is not overheating.

What you are observing when fast charging is called the Second Law of Thermodynamics. Anything that creates or uses energy does so with some loss. That lost energy is expressed as heat. So when you charge the phone it generates heat in the power source, heat in the charger circuit in the phone, and heat as the energy goes into the battery. The faster the charging, the more heat is generated. Likewise when you discharge the battery; not all of the energy from the battery gets to the circuits that use it. Some of it becomes heat. 

If you use the cellular network for voice or data, converting energy to radio frequency signals is very wasteful; only about 30% of the energy that goes into the network components comes out as radio signals, the other 70% becomes heat. And signal strength matters; a 1 bar signal requires that the phone boost its transmitter power to maintain a connection, and it isn’t linear. 1 bar uses 10 times as much energy as 4 bars. You didn’t mention your phone model, but an iPhone 12 or newer (including SE 3rd edition) with a 5G signal uses about twice as much energy as an LTE signal, and 5G towers are still not as densely distributed as LTE, so the signal is likely to be weaker, compounding the problem.

Thank you for participating in the Apple Support Community.

We want to make sure you reach the right team for help with your device. We recommend that you contact Apple Support directly. Depending on your region, you may be able to reach them here: Get Support.