Phone Screen Blackouts and respond only to Power Key Long Press
I just switched off my phone and then reboot in Fastboot Mode using Power + Volume Down key and then chosen recovery.

In recovery mode I choose Wipe and then Format Data then typed Yes and hit Go

This will take some time and the phone will reboot and now it's working fine.

Note : Take backup of data before formatting, you can take backup by connecting phone to your PC via USB and Copying all data on PC.