Freezing issue guidance wanted

Thanks for taking the time for the explanations Xaltar - great info and definitely helped me understand!

Unfortunately, although I think the issue might be partly thermal related, I'm not sure that's the full story. I did a test last night with the USB fan blowing across the components and although it lasted a bit longer, it decided to freeze eventually. 

I'm starting to think, based on a lot of other reboots of freezing, that perhaps either its not VRM heat related or that the VRM is very picky about the temperature and is tripping at lower temps than it should.

I'll probably be getting hold of the supplier of the motherboard to discuss options - either try a replacement or perhaps choose a different brand/model as I've read stories about boards that start off ok but fail after a period of months.

So, here goes.

Overheating can cause any number of issues from slow, choppy performance to hanging (brief freezing that resolves itself) to full thermal shutdown and being unable to power on the PC again until the components have cooled down.

* I'm assuming that the Overheat protection in the BIOS only refers to cutting out when the CPU overheats and not the VRM components as I did a brief test with that disabled?

Overheating protection (the setting) applies only to the CPU. VRM temps are not monitored by the UEFI. 

Yes, it would be normal to see all temps reporting as OK in monitoring software. As I said above, these temps are not reported. I would imagine because it would require a thermal sensor for each of the VRMs on the board which in the case of a 12 phase power design could be very expensive. Thermal shutdown/issues here are detected not by monitoring temps but by voltages going out of tolerance due to heat. Once the power controllers (chips on the board) detect this they trigger safeties to protect the system.

* Is there a particular temperature which the thermal cut-out triggered by or is the cut-out monitored by other factors?

Just reading back what I wrote originally I should have probably pointed out that 95% of the time freezing is a problem rather than rebooting and when the machine freezes sometimes it does carry on processing some stuff for a short time (e.g. once it froze when playing a video but the sound carried on playing for about 20-25 seconds before that froze too). Is that still likely to be a problem with VRM overheating as reboots seem to be the biggest symptom from things I've read rather than freezing? (It does sound like a good potential for the cause of the issue so not dismissing it but figured I'd ask the question :) )

Also just a few quick questions related to the overheat theory:

* I'm assuming that the Overheat protection in the BIOS only refers to cutting out when the CPU overheats and not the VRM components as I did a brief test with that disabled?

* Would it be normal to not see high temperatures in HWMonitor/BIOS HW Monitor screen following a freeze? (i.e. would the temperature spike and drop so quickly that you wouldn't see any evidence there?)

* Is there a particular temperature which the thermal cut-out triggered by or is the cut-out monitored by other factors? 

Thanks again everyone for their replies so far - it gives me great relief in having people to bounce ideas off and makes me more hopeful of solving my issue before I lose all my hair :)