6D won't turn on. What to do?

My 6D suddenly just stop working, then I turned it off and on and off, and the it was still on but it was frozen. So, I took out the battery, and it just won't turn on anymore. I checked google and it says to turn it off, take out the battery, the card, and the lens then press and hold the shutter button, or just keep pressing it. After like 10 minutes it came back to live. And just a few shots later it stopped again, and just won't turn on. And the same method doesn't work.

I would like to know if anyone could explain what happened to it? Like, what caused it to be like that so sudden? 

And please give some advice on how I can fix it on my own. Or do I need to get it to the shoo? Thanks