Overheating and battery drain

Merely using iPhone does not heat up the device. The question is

• What is the Health of the battery?
• Was it connected to counterfeit charging cable?
• Did your iPhone had protective cover which does not provide good ventilation?

Lastly, purchase Apple Products from an Apple Online Store, Apple Retail Stores, and many Apple-authorized resellers and wireless service providers.

Secondly, It is not clear here in your post about the ambient temperature in your area where you are using the iPhone. However --> Keeping iPhone, iPad, and iPod touch within acceptable ...

Store the device where the temperature is between -20º and 45º C (-4º to 113º F). Don’t leave the device in your car, because temperatures in parked cars can exceed this range.

Use iOS devices where the ambient temperature is between 0º and 35º C (32º to 95º F). Low- or high-temperature conditions might cause the device to change its behavior to regulate its temperature. Using an iOS device in very cold conditions outside of its operating range might temporarily shorten battery life and could cause the device to turn off. Battery life will return to normal when you bring the device back to higher ambient temperatures. Using an iOS device in very hot conditions can permanently shorten battery life.

Protect & Prolong life of your iPhone's Battery:

1. About the battery usage on your iPhone, iPad, and iPod touch ...
2. Batteries - Maximising Performance - Apple (IN)
3. iPhone Battery and Performance

Try some of these options too.

1. Avoid Screen Mirroring
2. Put on Low Power Mode
3. Put Auto Lock On (1 min):- with low power mode it will be 30 Sec
4. Put Auto Answer Off
5. Disable Push notifications for apps you do not use often
6. Keep your iPhone Face down to prevent notifications to light up screen
7. Enable Auto Brightness:- Settings > General > Accessibility > Display Accommodations > Auto-Brightness [Enable]
8. Manually lower brightness from Control Center
9. If you Want to watch continuous Video. Stream it on TV or a Monitor
10. Don't force close apps; Apps which are not on frontend screen are paused by the system to save energy. Apps require more energy to re-launch. Apps which are open in the background use large memory is a myth and quitting them is counterproductive
11. Location services to be allowed only while using the app
12. Set your iPhone to fetch email and calendar data from internet less frequently
13. Turning off Background App Refresh 
14. Charge before it drops below 20-30%
15. Try connecting to trusted Wifi where ever available in stead of Cellular
16. Enable Airplane mode in areas with bad cellular and wifi coverage. Your phone keeps trying for reconnection with the missing / weak network. This uses lot of energy
17. Switch off Wifi & Bluetooth while in Roaming or Not in Range
18. Enable "Wifi Assist" : Settings > Cellular or Settings > Mobile Data > Wi-Fi Assist [Enable]
19. Periodically Check your Battery Health (Settings > Battery > Battery Health)

Same overheating and battery draining issues after the recent update to 14.0.1. The phone will heat up spontaneously and get hot enough to be felt through clothing. My phone is an Iphone 11 pro — so not an old battery as one response suggested on this thread, My new Apple watch is starting to get hot on the charger and the battery drains in a half of a day. My 8 month old IPAD PRO has been working OK - doesn’t overheat - but is requiring a charge more frequently.

I did the suggested, full power down and restart, 3 times on all devices. That helped the connectivity issue but not the overheating or battery drain.

I contacted APPLE support and was told that they are ‘hearing’ these comments. But until they get enough of them reported it is a ‘non issue’ and most likely ‘user error’. Way to support users Apple.