Computer turns on and then shuts off after 20-30 seconds

I'm totally confused as to what is wrong with my PC. I was on the computer the other day and just like that, it decided to switch off. The first time i tried to power it back on, it ran a disk check (i've posted a screenshot of this in the link below). Now everytime i start it up, it switches on for a moment and then takes me to a screen full of options, i click on 'Start Windows normally' and then it switches back off. I've also clicked on the other options available but that doesn't change anything.

You can hear it power up and load, the monitor shows the 'Dell' sign. So there does seem to be life to it!

Where do i go from here? Do i need to replace a part? Do i give up and buy a new desktop?

If it helps, i've uploaded screenshots of how it looks from start to finish. The first screenshot is of the disk check it ran the first time (not again since). The other screenshots are images of how it looks from the first step to the last: https://imgur.com/a/f3aZ1

Any help would be really appreciated!