ive had this issue some times but never the same solution.
one fix was i disassembled the entire computer and put it toghter again and it fixed it. i still dont know what was wrong. but this is just typical
another time i think i used older PSU with too many HDD's (not ssd) it started to act like you descripe. i tried disassemble. didnt work. then i disabled all drives apart from the C: HDD and that fixed it.
theres so many reasons, first id disassemble your comp and put it toghter again making sure all plugs and cables are connected correctly. if it still have same issue, id disable all the devices that you dont need for the comp to start up, like CDROMS, extra HDDs and so on. if you have on-board GPU then disable your graphics card as well.
if problem STILL persist, yeah then id say PSU game over OR you need to dust it off
