Chosen Solution
Unfortunately that looks like a GPU failure. If it’s an A1369 from early 2012 it’s a typical issue, less frequent on 2012 A1466 but it may still happen. You can download and run a benchmarking App like Valley from Unigine, that would cause a repeated reboot or shutdown as soon as launched and would confirm the GPU failure. I’d recommend backing up your data before that, as the board may brick for good anytime.
I have this problem with my laptop and I was thinking out just soldering a new one to broad itself. Bc I try repasting and and look up what can cause this and every thing says it the GPU or CPU chip that is the cause of it. So if the chip is failure maybe just solder another to it.
