Q: Why facetime needs activation if the phone restarts

Hello Mansurk4,

Thanks for using the Apple Support Communities!

If I understand correctly, Facetime is asking to be activated every time you restart your iPhone.  I use Facetime a lot also and know what a great App it is.

The first thing I would recommend would be to force quit the FaceTime app. Then, start FaceTime again, activate it, restart the iPhone and check to see if you are asked again.

 Force an app to close on your iPhone, iPad, or iPod touch.  

If it continues to ask you to activate FaceTime, be sure you have a current backup of everything on your iPhone.  Nothing I am going to suggest should cause any data loss, but it is always a good idea to have a backup.  If you follow the link below, you will find instructions on how to do a backup.

How to back up your devices using iCloud or iTunes.

It is possible that something has become corrupted that is causing the problem.  Once the backup is finished, I would suggest to reset all settings.  Reset All Settings resets preference files that may be having issues. This step will not delete your contacts or photos or any personal information. It does remove all of your preferences for Wi-Fi, Bluetooth, Do No Disturb, Notifications, General, Sounds, Brightness & Wallpaper and Privacy, and removes your Touch ID & Passcode.  Reset All Settings by tapping Settings > General > Reset > Reset All Settings. 

Once the iPhone comes back on, activate FaceTime one more time and see if you asked to activate again after restarting the phone.

Cheers!