Please try holding the Home & Power keys until the Apple logo appears on the screen, this will perform a soft-reset of the device.
If you still have issues, the only other thing I can suggest is a hard reset, which will delete everything on your iPad, hopefully you have a backup?
To do a hard reset go to: Settings-> General -> Reset ->Erase All Content and Settings
Once device has reset, set it up as a new device - try it and make sure it works ok.If it does and you have a backup proceed with restoring, if you have backup on iCloud you can repeat the above 'Hard Reset' then once device has reset again choose Restore from Backup. If you have issues after restoring there is likely to be an issue with your backup.