Sounds like the GPU needs to have its Thermal Paste or Thermal pads replaced or the GPU fans are not working.
Try running OCCT GPU Stress test and see if it shuts down the PC or stops the test with an error due to overheating.
If it does then I would open a Warranty Ticket, if the GPU is still under warranty, to have the GPU card checked.
If not under Warranty then I would try to replace the Thermal Paste and/or Thermal Pads and see if the overheating continues.
But if the GPU fans doesn't turn on while doing the stress test then you would need to replace the GPU fans