There may be several reasons for WHEA fatal hardware error:
Most common cause of WHEA fatal hardware errors. It can be a malfunctioning CPU, RAM, GPU, motherboard, power supply, or any other hardware component.
Outdated or incompatible device drivers can also lead to hardware errors. Make sure all your drivers, especially those for critical components like the GPU and chipset, are up to date.
A malfunctioning power supply can cause voltage fluctuations and result in hardware errors.
Make sure there is no over heating.
If you're overclocking, revert your hardware to default settings and see if the error persists.