First thing, make sure your drivers are good. Do a clean install of the graphics drivers.
Remove and re-insert the graphics card. Make sure it is going in the slot without undue stress.
If you have managed to get the motherboard installed slightly crooked the GPU may be loosing contact with a PCIe pin when it heats up.
IRQL NOT LESS OR EQUAL is also a sign of bad memory. Either System or VRAM, but it can have many causes, including power. So if you have lots of memory you can try reducing the number of sticks, then re-installing and increasing the voltage if that was the problem.
Can't rule out a faulty GPU either.