First question is you monitor plugged into the GPU or the mother board? It needs to be plugged into the GPU.
Next did you plug in 8 and/or 6 pin power connections to the GPU? It has to be fully hooked up.
Next if all that is fine does the power supply meet the minimum power requirements for the GPU card?
You can try the GPU in another PC and see if the problem follows the card, then you know it is the card.
If you have a spare hard drive you could fresh install Windows 10 to see if it is an issue with Windows 10.
Another thing to try is unplug anything USB except the mouse and keyboard to make sure no other peripheral is causing an issue with the boot.
Good Luck!