How can someone stop "Android is starting"?

[AC Question]

My phone has been on "Android is starting" fro about two hours now and it won't stop. want to know how to stop it.

 

[B. Diddy]

Welcome to Android Central! Which phone?

 

[Adam Shwartz]

My phone is Nexus 6P. Its been on "Android starting" for 3 hours. I tried restart, turn off, restart is safe mode.