I would suggest taking it to an authorized Samsung Dealer and have them take a look at the power supply. I have a Samsung Galaxy phone with a removable battery that would restart and restart and didn't boot I did a factory reset the problem continued. I took out the battery and rubbed the contacts lightly on a piece of fabric then re-installed the battery, it worked perfect. The only issue with your tab, no access to the power supply. Good luck i hope you can get it fixed.