[sAmI]

I think what I would try if you know someone with a pc that can use the same ram and swap it out and see if you can run ram memtest on it.

In your system settings (or whatever it's called on windows), does the system report the proper amount of RAM?

Your PC could be overheating but unless the thermostat is broken you should be able to check your cpu temp. Also, if it's overheating I think the pc will simply turn off, not freeze or hang.

Also, as you seem to be comfortable working inside the pc, you might try just buying a stick of ram (buy one with a good return policy) and test it out. If the new ram solves your problems you can avoid an expensive repair bill. If not, return the new ram and maybe consider sending it for repair. Although I wonder: the i5 is a somewhat dated processor... it might cost more than the pc is worth to have it serviced.

I actually got my hands on 2GB Sk Hynix memory turns out to be it was way too bad than my own and corrupted my whole OS, yes it does report proper amount of RAM and even it works fine for many hours.
I was thinking to get my hands on a RAM but the market seems to be closed for a short time i'm waiting for that the repairing shop is somewhere yes open. I'm ofcourse gonna buy one but i am trying to be sure if its actually the RAM issue i can't waste a good 8GB stick and if i buy new one turns out it gives me the same issue. Yeah i'm pretty comfortable in building PCs and all.

If I'm not mistaken there is lifetime guarantee for RAM. So you can just send your RAM to the repair station and get the repaired one later. If it's already soldered to the laptop/PC, Idk .

The lifetime guarantee on RAMS in Pakistan is on branded rams (Box-Packed) like HyperX FURY etc etc they give like 5 years warranty or so. 

Of course before you send your RAM for repair, it is always better to try replacing it with another piece of RAM (if you have it) first.

But because your PC works fine after you do not use it for hours, it might be a power supply issue.

So I would suggest you to try replacing the power supply to see if it makes any difference.

I'm also give it a try on Power Supply but honeslty it is giving me BSOd's which indicates actually Memory issue i have a GTX 1060 3GB in there as well though with a Antec Earthewatt 500WATT (I know not really a power supply but kinda working for me well), I'm surely gonna give it a try!