with respect , if your laptop sometimes doesn't even turn on then this is a hardware fault and could possibly be RAM thats gone bad, faulty CPU or hard-drive
To determine if its the ram try and borrow a single stick from a friend and see if you can get your system to consistently boot past bios screen ?
The first task is to get it consistently booting to post, and persistently booting into windows with a faulty component risks damaging your windows install to the point you cannot repair it and will need a fresh install ?