Confounded with this t210r

I am trying to fix this t210r tab 3 7" for my mother-in-law. I have no idea what's wrong with it. Out boots up, loads into normal os but then in 5-15 seconds it reboots. Factory resetting it in recovery mode does not actually reset it, not sure how that works... can't root or install any custom roms or kernels. I've tried five or six from this site. If I try turning on usb debugging once it restarts, any changes made are no longer present. I've run out of ideas. Can anyone help or offer any suggestions?
Thank you very much.