I got an answer to my problem with my Samsung Galaxy GT-N5110. Replacing the battery with a new didn't solve it. I later removed all key pads (power, vol+, vol-). It started working well somehow. I then checked the flex the power, vol+ and vol- were sitting on. The power pad was weak and broken. Because of this the power button was permanently On. This was confusing the Tablet which made it to recycle the power On.
Solution: I changed the flex that control the power, vol+and vol-. It's a single flex which I bought online. This solved the problem. For about five months now the Tablet has been working as before. Pls check that flex and replace it. Hoping that there is no other physical damage on other ports.
Pls note-if you're not a Tech man like me don't try it. You may damage other tiny components on the board. Let a Tech man help you to fix this.