Try turning it on in "Safe Mode" and see if it will load. If it does, you won't be able to access a lot of things, however you will know that there is something on the tablet that is hindering it starting normally. So I would then check for bad apps, viruses, malware, etc. Worst case, you have to "Hard Reset", but that is a last resort option as it will wipe everything you have on the device.
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.