Question PC shuts down by itself, doesnt work, then the next day it works normally ?

Apr 20, 2023
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I have a Lenovo Pre-Built with the following specs:
Intel Pentium E5800 3.2GHZ Dual Core
4GB DDR3
A seagate 3tb hdd, and WD 500GB HDD
and AMD HD8490 1GB
240W Liteon PSU

The GPU did not come installed and i installed it myself, it had worked fine 4 months but recently been giving issues, it would randomnly turn off and upon pressing the power button, the fans would spin for a second and the power led would turn on then go off again, but after leaving it for like 3 or so hours it would turn on and work for 30mins then do the same thing again, but after leaving it for like a day it would work normally for 4 or 5 hours and do the same thing again.

I also want to say that I actually installed an AMD R5 240 in this, that worked fine for 2 or 3 days and then the PSU went bad, then i changed the psu to another 240w one and installed the hd8490, is it possible that the psu went bad? the hd8490 isnt even very demanding and a 240w psu can easily run it then why these issues? the psu choices are limited because this pc is a sff, if i were to get a 300w or 350w psu it would have to sit outside the pc case. please help me