Hi. By re flash, do you mean a hard reset either from the main menu (under settings) or via the recovery mode or you mean that you literally flashed in a new ROM or firmware with no success? If the first is the case, then you will need to try flashing a firmware or ROM, but if the latter is the case, then you may sadly be looking at a weak battery due for replacement (though this may depend on when the reboot occurs while the tablet is in use or not). Let us know.
Signature: SA tech Q&A is a free question and answer site. If the answer/solution provided above does not help' please use the reply button below to request further assistance.