frozen phone
I have an Iphone 6 plus. It keeps freezing up on me.
It all started when I updated to the most recent version.
Obtained a new replacement phone, and it does the same thing.
See this for dealing with a device that is frozen, If your iPhone, iPad, or iPod touch won't turn on or is frozen - Apple Support
If you continue to have this issue, it would lead me to believe there is a problem with your backup, since it continued on a new device. You may be better off restoring your phone to factory and setting it up as new, not from a backup. Restore your iPhone, iPad, or iPod to factory settings - Apple Support