Recently my Venue 8 has been suddenly powering off while I'm using it.   Both recent times I did note that the battery still had around 60% life left in it before I started using it.   I used it for about an hour each of the last two times it shut down.   Once it shut down, it would not power on again until much later.

I really need some direction on this issue as I don't have a clue as to the cause of the problem.