First please post your PC information with your next reply.
When you boot up the computer during POST does your GPU fan turn on for a second or two? (Check to see if GPU fans are working or not).
Do you have a GPU Trouble LED lit up on your Motherboard or a Digital Trouble Code showing? (Checking to see if Motherboard finds an issue with GPU card when booting up).
Download free software OCCT and run all three tests, CPU, GPU, and PSU. Observe to see if your GPU fans turns on while under heavy stress and see if it starts overheating or not. Keep an eye on Temperatures, Fan speeds, and PSU Outputs.
If the GPU fans don't turn on while under stress and it starts overheating stop the OCCT test. Either you have defective fans or the power to the fans is broken.
Physically check the fans that they turn without resistance with your finger and no noises.
Also make sure that the GPU PCIe Power cable is making good contact if it has one.
If still under Warranty I would open a Warranty ticket.
NOTE: Your RX580 2048SP is a GPU card made exclusively for the Chinese market and it is actually a Rebranded RX 480 GPU card with slightly different speeds than a RX480.
