iPhone 6 display hanging while using iPhone
Display hanging
Try a forced retart of your iP6:
On an iPhone 6s and earlier, iPad, or iPod touch: Press and hold both the Home and the Top (or Side) buttons for at least 10 seconds, until you see the Apple logo.
Then test again.
If nothing changes, contact your nearest Apple Store and have your device inspected.
Regards
Giulio
iPhone 6 display hanging while using iPhone