This problem has been deemed a hardware issue, particularly on the Wi-Fi chip that gets too hot when performing any iOS updates over Wi-Fi.
Responding to this concern, we've created this article with workarounds that will help get the main problem fixed.
Follow these steps to fix the issue:
1. Restart your iPhone. This method is also called a soft reset -- one of the first steps in troubleshooting a device without affecting data. Here's how:
a. Press and hold the Power button located on the upper edge until the slide to Power Off appears and then release.
b. Slide the Power switch right. Wait for a few seconds for the phone to power off.
c. With the device is completely powered off, press and hold the Power button until the Apple logo displays then release.
If your device will not respond or restart to any input, press and hold the Power and Home buttons until the Apple logo appears then release.
2. Verify Airplane mode settings and make sure it is disabled or turned off. Just go to Settings and then select Airplane Mode.
3. Reset network settings. To do so, tap on Settings->General->Reset->Reset Network Settings. Doing so will reset all network settings including Bluetooth pairing, Wi-Fi passwords, VPN, and APN settings.
4. Ensure your device is running the latest iOS firmware, otherwise consider performing firmware update. Every time Apple rolls out an update, it contains bug fixes and performance enhancements.
If problem persists, either you may opt to restart your iPhone or contact Apple support for further troubleshooting and recommendations.