Asrock Z370 Extreme 4 BIOS/Boot Issues

Normally I hate being vague in the title post, but not sure where the problem is here. So will run through all problems not just BIOS.

System

Asrock Z370 extreme 4
Intel 8600K
EVGA 1080Ti SC2
16GB 3200Mhz Corsair Vengeance memory
Windows 10 on a Samsung 970 Evo 500GB M2

I'm getting seemingly random BSOD's when running some games so I started to look for causes. Windows won't create a dump file, settings are correct to do this. So I started widening options, the BSOD's vary in message so decided on factory reset as stage 1 to see if the would allow dump file to be created, as I can't figure out root cause without at least some clue from dump file. One of the BSOD errors is unexpected store exception for example, which could be hardware related.

What I have found is the PC won't do anything in the period between switch on and Loading Windows. The PC hangs if you try. Fast load is off. Swapped out Corsair keyboard for standard one in case it was driver issue with that, no luck.

Issues so far
Dump file creation hangs at 0% completion.
Pressing F2/delete to enter BIOS hangs PC until you press reset then it boots into Windows ok.
Factory reset Windows hangs the PC after notifying of restart. Does the percentage count down then screen blanks.
Trying to restart to BIOS from Windows restart hangs pc.
Trying to restart to safe mode from Windows hangs PC
Unable to Boot from USB drive, not recognised in Windows Restart options. Drive is recognised in windows.

Normally I would have just done a complete Windows wipe and reinstall, but the inability to get into the BIOS has me not wanting to go there yet. It's only games being affected with the BSOD's so they have become a secondary consideration at the minute.

Anyone with a fresh set of eyes see anything I am missing. Brain has stopped working while trying to figure whats going on here.