Please update with new improvement. My phone restart when make or receive call on Android 7.0 but on Android 6.0 not restart. i was factory reset but still restart. Thanks
This is a software-issue with the screen - it lets the device restart if the screen is touched for long time - in your case with your ear during a call. A clean flash
of the latest firmware should fix this.
Please tell us if it helped and if you have further questions.