Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Your tablet uses the Android OS of version 4.X.x I presume. If so, it may be that the Android OS has become corrupted to the point where it will not boot up fully and restarts instead.
(It could also be, that the tablet's hardware is severely defective, not the Android OS, and that the restarting is only in response to a fatal error or very severe error in the hardware rather than a fault in the Android OS.)
To try to fix the tablet, a 'factory reset' or 'hard reset' would be the advisable thing to try. However, be warned first: a factory reset wipes all your individual data and configuration and settings, stored on the tablet, off of it completely. Would you find that allowable?
I also should ask: How old is the tablet in question? was it ever dropped, or gotten wet, or otherwise treated badly?
Let me know, and I will instruct you further. Thanks.