mbp frozen on start up screen

I have a mid 2015 15” MBP which I use with an external monitor. Out of the blue both screen froze with distorted images and upon trying to restart the mac it gets 3/4 of the way through the screen flickers and it comes to a standstill. I’ve tried all the various reboots, safe modes, recovery etc but nothing.

this is where it’s freezing in verbose mode-

any help would be greatly appreciated