Q: sierra logs out on his own. then im not able to log in again, that i have to restart. happened 3 times

**** M44taskin,

Thank you for using Apple Support Communities. It's my understanding your Mac has been unexpectedly logging out on it's own. I can certainly see how this could impact your usage. I am happy to help. It's possible that your Mac has been configured to automatically log out of the user account when inactive. Please try the steps below.

Use these steps if you don't want to be logged out automatically:

1. Choose System Preferences from the Apple menu.
2. Click the Security & Privacy icon in the System Preferences window.
3. If the lock icon shown in the lower left corner of the window is locked, click it and enter an administrator name and password.
4. Click the General tab.
5. Click the Advanced button.
6. Deselect the option, "Log out after __ minutes of inactivity."

 

If the Login window unexpectedly appears on your Mac

Have an amazing day!