Hi, welcome to Android Forums, I'm rabidhunter.
Sorry to hear that your tablet keeps shutting down. Without knowing the specifics, my best guess is that your battery is not fully charged. My recommendation is for you to charge your tablet for a couple of hours, then try turning it on.
I would need to know more information to help you. What is the make and model of your tablet? What was the last thing you did before your phone wouldn't turn on?