Keep shutting off and it has good charge

Go to "Settings" and look under "Display & Brightness" on left side of screen. There you will see "Auto Lock." It may be set to "Automatically" Lock after 5 minutes. You can change it there to auto lock (shut down) from 2 minutes to "Never" if desired.

sounds like the battery is not charged up or taking a charge, check to see if the adapter is putting out voltage at the plug/pins.

Please make sure the tablet is charged for at least 4-6 hours. Also, make sure the correct button is being used, oftentimes we hear the back or home button has been used in error. If the issue persists, you can try performing a power reset. There should a power reset button near the charging port. It looks like a tiny hole. While plugged into the charger, use a paperclip to push the button inside this hole for 3-5 seconds. If it turns on, please allow it to charge for 4-6 hours before using it. If you leave it on the charger for longer than the allocated time, you will go back to having the same problem as before. If the power does not come on, please leave it plugged up for 4-6 hours then disconnect it from the power and turn it on.

If your tablet does not have the reset button: With the tablet plugged into the charger, hold the power button for 10 seconds then click the volume up once. If it turns on, please allow it to charge for 4-6 hours before using it. If you leave it on the charger for longer than the allocated time, you will go back to having the same problem as before. If the power does not come on, please leave it plugged up for 4-6 hours then disconnect it from the power and turn it on.
Support Troubleshooting Guide

specify weather it is plugged in or not when this happens and if the battery is above 30%
if plugged in, is the plug getting loose if so replace the wire that charges it and plug will be tight again . clean around plug with folded paper corner to be sure nothing is inside pressed to back of plug slowly shorting power. batteries do wear out in these things so only plug back into charge when it is below 20% and let it charge all the way up. as each partial charge cost you one of the 1000 charges in the battery's life. get Battery Doctor from the play store it will trickle charge at end of cycle and will tell you the battery's health. good app.

Have you checked to see what the battery percentage is at when it shuts down?

Make sure to give it a really good first charge, and don't play any games while it's charging and low on power. Many of these new and intense games can actually kill the battery faster than the charger can charge it.

Charge unit and if a reset pin hole in cover reset unit using a small pin or needle GL

Set the auto lock for 2 minutes. Keep in mind that the iPad will not auto sleep and lock during certain application evolutions, like video, game application etc.

if it's just sitting at the spring board, it will auto lock at the specified time interval. imthemobile guru

Happened to me today. Fix: Boot it up and go to Settings > Backup & reset > Factory Reset: Check the Erase SDCard Data Box. Make sure you backup all your important information to the External SDCard first using Astro or something. Enjoy your fixed tablet after rebooting again and going through the Wizard for the Last time.

Remove the rear cover...use your fingernails, or something thin and plastic (like a guitar pick) to get it started, then work your way around unsnapping it until it is off. Now unplug the battery, the battery connector pulls up towards you to unplug, it snaps in. Now, you have to put the rear cover back on..because as you will notice there is foil on it, and pins on the board that ground through that foil. After the cover is back on...press and hold the power button for 30 seconds or so to completely discharge the energy from the board. pop the back cover off, plug the battery back in, put the cover back on...and plug the tablet in. Now when you push the power button you should see a battery charging icon...let the tablet charge for an hour or so...then boot it up if you would like, but let it charge to 100% before unplugging. Good luck!!