u/obrx8

not sure if this is fine to post here since this one is not a new build.
So, yesterday, while i was just editing a video, my pc suddenly shut itself down.
Thought there was something wrong with my psu so i removed and reconnected all the cables, it still didn't power up. tried removing everything but the cpu and ram, and it somehow works. but the moment i put in my gpu (with the psu cable unplugged), the motherboard just flashes for a split second then turns off completely. then if i plug in the psu cables, not even the mobo led flash happens.
right now i have everything back on except the gpu and just using the integrated graphics, but i'm worried that if i bought a gpu, and the problem lies with my psu, it would be a waste, since i could have just bought a new psu and tried if my gpu still works.
is it possible that a psu can suddenly stop loading what it can previously?
also another thing happened while typing this, pc froze, black screen then resumed working again. which never really happened before. (just assuming this is just a driver issue, hopefully)

specs:
cpu: 3400g
gpu 1060 6gb
psu: seasonic gx 550w
ram: 16gb ddr4
mobo: msi mortar b450m
built it myself and been using it for almost 6 years. but the gpu was a second-hand one so i don't remember how old was it.
(i have a shit pc yes, but i only use it for light gaming, and mainly for work)
thank u!