Question Trouble turning on laptop

Apr 2, 2019
I have a GP62MVR 7RFX Leopard Pro on which I have installed a 8Go RAM stick, with windows 10 Pro.
Processor: Intel(R) Core(TM) i7-7700K CPU @ 2.80GHz
Graphics Card: NVIDIA Geforce GTX 1060
Hard Drives: B: 931 Go (704 Go free) C: 237 Go (146 Go free)
Antivirus: Avast (free version), updated.

For the past 3 weeks I have had the same problem :
When I boot my computer, the light of the power button turns on, but the computer doesn't boot at all. In this case, I can still hear the cooling fan turning inside the case, and I can still activate the second fan with the associated button. The only thing I can do in that case is to use the power button to turn it off.
Sometimes when I boot the laptop, the backlight from the keyboard turns on and the computer do boot, it shows the MSI logo (before the windows logo), shuts down, and boot back again with only the power light turned on.
If I am lucky, it justs boot up normally. (and after extensive tesiting, it seriously looks like nothing affects it and it's just pure luck).

I have tried to take out the battery and discharge the internal current by pressing the power button for 2 minutes, with and without the charger, it doesn't seem to do much at all.
I have tried every combinaisons with the RAM sticks, (one at a time in every positions).
Something odd that happened : I emptied my SSD that was pretty full and for almost a week the laptop booted with no problem.

I fear it's the motherboard, but I'd like a second opinion before sending it to repair. Thanks alot.