First, try to do a full backup—reset—restore of your iPad via iTunes. (a) Plug in and, if it doen't start automatically, run iTunes, (b) back up your iPad, (c) do a total reset, (d) restore this last backup.
If this is enough, just go ahead and do it.
Otherwise, do like me — dummy — and read the excerpt from Apple's KB below:
(...) You will need to restore your device using the computer with which you last synced it. This allows you to reset your passcode and resync the data from the device (or restore from a backup). If you restore on a different computer that was never synced with the device, you will be able to unlock the device for use and remove the passcode, but your data will not be present.
If this does not work, (and probably won't, but it's a 5-minute operation), then you should seek hardware assistance. If it's a brand (or almost) new iPad, go back to the shop and they will give you a new one, without much trouble... It use to happen with iPods and exchanging the product was routine in this shutoff—restart issue.
Guilherme R Basilio