> It turned on and five seconds later it turned off automatically.
Did the screen backlight turn on at any point in those five seconds before the laptop turned off?
If not, from your description it sounds like you're in a "reset loop" in the RAM initialization stage. The firmware tries to initialize your RAM, fails for some reason, and resets (reboots) to try again from scratch. If it's never able to initialize the RAM correctly, it will turn off and back on forever.
Resuming from suspend-to-RAM could theoretically trigger such an infinite reset loop, but I've only ever seen it when I modified the order in which coreboot clears the resume flag and initializes RAM. The way the firmware works normally, resuming from suspend should only affect the first RAM initialization attempt. So I think there may be another cause here.
I would first suggest checking your memory modules to make sure they match in density and such (the easiest thing to check is the RAM part numbers). Since you've already tried disconnecting the NVRAM/RTC battery, I guess you know how to get to the RAM slots right next to it.
