Firstly, thanks to all for the inputs.
Yes the warmed up part is exactly what i've been thinking of. Thing is this is a pretty old PC which is why i was suspecting the Motherboard as well.
Anyway, i'm gonna get a CoolerMaster or Antec PSU in the next few days to see if that solves the issue.
Given the PC's components, it makes more sense to buy/build a new PC if it is indeed a motherboard issue. (no SATA, no PCIe, P4 processor, DDR support only etc)
Also, there's another thing i'm having trouble figuring out. Maybe you guys can shed some light on this:
I was preparing for exams a month ago when this problem (opening post) started showing up. I tried my best to solve it then but gave up after a week so that i could focus on studies. For the next 2 weeks, the PC remained unused. I didn't even try to turn it on once.
After 2 weeks, I took apart all the components and checked for dust. I put it back together after cleaning out what little dust i could find. When i turned it on, it worked perfectly without any hanging. It's been another 2 weeks since then and the problem seems to have reappeared and i know it's gonna get worse in the next few days.
So, what do you guys think? Did this 2 weeks of inactivity somehow resolve the problem. I checked for leaky caps btw and found none. Not sure how to check for raised caps. I'll google that to find out.
My PC may not turn on tomorrow so i'll post an update after i install a new PSU.