Is the software on your Tablet up to date? Go to Settings > Software update > Download and install. Also, let's try a Soft Reset. This will end all processes and give the Tablet a fresh start. Press and hold the Volume Down and Power keys at the same time until the Tablet switches off and back on again.
Let us know if this helps at all.
Have you tried restarting the tablet with the previous steps? Also, have you been using an official Samsung charger to charge the tablet? From Samsung Members app, go to: Get help > Phone Care > Interactive Checks > Battery. Is there any action required showing after the test? Here also are some tips to help lengthen and improve the battery life of your tablet:
-Turn off Wi-Fi when it is not being used
-Turn off Bluetooth when it is not being used
-Turn brightness to auto-brightness
-Close apps once you have finished with them, don't leave them running in the background
-Remove widgets and disable any live wallpapers on your screen