MBP repeatedly hanging then shutting off completely

Hi all 🙂

I've had to send my TouchBar MBP in for a warranty repair as the USB 3 circuitry on one of the ports has failed (USB 2 circuitry works fine and I can charge the computer through the port) ... very strange problem.

Anyway, I've been given a Mid-2014 MBP 2.5GHz i7 machine as a loan computer and it's giving me no end of problems with hanging and then completely shutting itself off.

I can't pin-point what programs are causing it to happen. Sometimes I can be working for hours and all is well, other times it will crash and turn off, and then 10 minutes after rebooting the same thing happens again.

Where can I find the most useful crash logs to try and diagnose this problem? The machine is running High Sierra 10.13.2 but I'm planning to imminently wipe it and reinstall Sierra in case this is the cause of the problems.

Any advice / pointers you can give would be greatly appreciated. I hope to only have this machine for a week to 10 days, but it's my main work computer (as a photographer) and the crashes are a real pain.

Many thanks for your help,

David 🙂