1. Hard restart iPhone
Maybe you have tried this method, indeed, this operation applies to many situations including iPhone frozen or crased after iOS 10 update. If you haven't do anything on your iPhone, you can try it first.
Just press and hold down both the Sleep/Wake button and the Home button at the same time. Keep them held down until you see an Apple logo. Then let go.
2. Plug into a wall outlet
It is not a joke. You iPhone may run out of power during iOS 10 update, so try to charge your iPhone for 10-15 minutes. Then see what happen. if it resumes and try a hard reset to make sure.
3. Try a free third party software
Another very simple way needs a totally free tool - Reiboot. This PC-based software can help you fix iPhone frozen during or after iOS 10 upgrade. No need to restore with iTunes and no data loss.
Download and install the Reiboot on your computer, then connect your iPhone to PC with USB debug. Launch Reiboot and it will detect the condition on your iPhone, you can see "Enter Recovery Mode" or "Exit Recovery Mode", click on the button according to your situation to fix iPhone frozen after iOS 10 upgrade.
4. Restore your iPhone with iTunes
If you've been backing up your iphone, you can restore your iPhone in iTunes. Hope it can help you.
5. Try a paid third party software
If the methods above cannot help you fix iPhone freeze after iOS 10 update, you need an iCareFone to help you repair iOS system which can reinstall the system without any data loss. Just give it a try!