You might want to try starting it up in "Safe Mode" and see if it loads. If it does, then you most likely have something on your tablet (malware, virus, bad app, etc.,) that is the cause. Or a recent update to anything on the tablet. You would need to remove, uninstall, clean (for virus, etc.,) whatever is the problem and then reboot the tablet.
If that doesn't work, or it won't start in "Safe Mode" you may have to do a "Hard Reset", but that you should really save for a last resort as it will wipe all your personal data and you can't get that back.
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...