Try starting it up in "Safe Mode" first and see if it will load. If it does, then you just need to find and remove the problem. Bad app, virus, malware, etc. If it won't even do that (go into "Safe Mode") then I would try the "Hard Reset". Just note that doing so will wipe all data on the tablet.
To get into "Safe Mode" please do the following.
1. First turn off the tablet.
2. Next press and hold "Power" until you see the manufacturers logo on the screen, then release the power button.
3. "Quickly" press "Volume Down" and hold it for few seconds until you see the message "Safe mode: ON" or something similar.
4. If you wanted disable it, simply repeat the steps above, and you should see "Safe Mode: OFF" rather than on.
NOTE: Doing...