Predator Laptop Won't Boot: Cycles Itself On and Off Every Few Seconds PH315-51-78NP

Hello everyone. I'm hoping someone here can help me out with this. The gist is that I'm afraid to shut down my laptop because I'm worried it will never turn on again.

I have a Predator Laptop Model PH315-51-78NP. I recently started having an issue with it booting up. The symptoms started a few weeks ago when I tried to power it up. I had it it plugged in but it did have a low or dead battery. After pushing the power button, it would start up for 1 or 2 seconds, this included the keyboard lighting up and the fans spinning, and then it would turn itself off. Then it would turn itself back on only to turn off again. This cycle would repeat on it's own. After a minute or two it finally booted up into windows.

I didn't think too much of it and wrote it off as a low battery issue. But it happened again a week later. This time it would not boot into Windows no matter what I tried (eventually it did and I will get to that part at the end). Occasionally it would stay on long enough to show the white Predator logo but would shut down before I could do anything. It was never long enough for me to get into the BIOS. I tried everything I could find on this forum to fix it and I also took it to a computer repair technician. This included:

1. Looked for any buttons on the bottom that would keep the laptop from booting if it wasn't secured tight enough. My laptop doesn't appear to have any of them.
2. Switched/removed the RAM. Used each stick in only one of the slots. I also tried a different set of RAM. I'm highly confident that I eliminated RAM as the culprit.
3. Held down the battery reset button for 1 minute.
4. Held down the power button for 1 minute.
5. Disconnected the battery and ran off the power plug only.
6. Disconnect the power plug and run it off the battery only.
7. Disconnected the hard drives and tried to boot it.

The last thing I did was turned it on and let it do the on/off cycle for an extended period of time. Amazingly after about 2 hours, when all my hope was lost, it finally booted into Windows. This was a week ago and now I'm terrified to shut it down. My concern is that the motherboard is messed up. Has anyone else experienced this? Do you have advice/diagnostics I can try now that it is in Windows? 

Thank you!