Notification bar, home and recent tabs not working in Nexus 6

[Android Central Question]

Since yesterday I am unable to pull down notification bar. Home n recent tabs not functioning as well. My handset suddenly switched off 5 times as soon as I switched on it and this problem started. The handset is getting switched off suddenly since last few months .. what can be done to resolve the issue . It is almost 3 years old

 

[B. Diddy]

Welcome to Android Central! Does this still happen in Safe Mode? https://support.google.com/android/answer/7665064?hl=en