Device powers off almost immediately after starting topic

So, I have had my shield tablet for about a month now and people have said the tablet has random power off issues. I never noticed this, but around 3 days ago my device started acting slightly wierd with it being slightly slower than usual. Then, when I checked my device about 3-4 hours later. It was off, I powered it on and then it instantly shut off. I turn it on again hoping to see its chrage level and I did and it was at 68%. So I reset it using my cwm recovery and for about 15 minutes it was fine, then it shuts down again and does the same thing. So today I reset it using the imgs from nvidia and it works fine. So I go and update to 4.2.1, still work. Update to 5 and it just breaks again.