Usually there´s the Post screen with some of the PC info or just the pc/lap manufaturer screen, then it goes to the loading OS screen
I can make a (possible) list of the problems - I could say more if I actually saw the pc starting..
(whoever else is reading may also add to the list)
bad psu (power supply unit),
some psu cable is a bit offplace (this happens a lot here in Brazil in summer)
the CR2032 battery went bad (the most simple to solve)
The best way to locate the problem would be to dismantle all the pc, clean memories and video card contacts, and start from the basics - mobo, cpu, psu memories and video card (if needed), then moving to the other devices. I do NOT recommend this if you don't know that you're doing.