Why is my Asus tp500la not turning on all the times?

my Asus turns on and failures in a random way, sometimes it works well, but other times the notebook just turn on for a few seconds and then turn off suddenly, without turning on the screen, and only turns on two LEDs at the same time: the "plane mode" and the "bloq num"...when the notebook turns on with this two LEDs, I know it will turn off at the next second. I already checked the only ram that I can access, because the other 4gb ram I don't know where it is. At least all that I can see seems well connected to me