Try starting up in "Safe Mode" and see if it will load correctly. If it does, then you probably have something on the device that is causing the problem. Bad app, malware, virus, etc. Which you would have to remove to get it to work correctly. If, however, it won't load in "Safe Mode" either, then it may well be hardware. Unless the device has been rooted. And in that case that I can't help with as it alters the system. You would then have to try posting in the rooting forum to see if they can help. Yes that forum says it is for phones, but they use the same OS as tablets, so they should still be able to assist, if it was rooted.
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.