Is my motherboard the issue?

Hello,

I have a X99 Extreme4 motherboard with an i7-5820k that I wanted to resell as I got it very cheap online. I wanted to put everything into a newer pc case and sell it that way with a gpu like gtx 1660 super.

Unfortunately i don’t get any imagine when I connect the gpu through hdmi but the fans spin . I tried the gpu on another motherboard and It goes to the bios. I also tried another gpu on that issue motherboard and still no image.

Everything else works and spins fine .

When I start the computer, it works 2 seconds, then shuts down and starts again all by himself and then it works but still no img. What does that mean?

Is my motherboard dead?

Thanks in advance !