Why is my screen freezing during start up?

Hi there, I am currently trying to fix my old xbox elite s but really struggling to find the source of the issue.

It is basically freezing after the start up logo (leaving a white screen) or during the logo (@%^ the 'x' is moving across the screen.

I have taken out the HDD and it has never been placed in a confined space or anywhere that blocks the fans. I am happy to take it apart and repair it myself - I am just unsure which part needs replacing.

If you could please help point me in the right direction regarding parts/how to guides, it would really be appreciated! :)

thank you for reading, Jonny