Chosen Solution
I recently replace my screen assembly on my Iphone 6 plus and now when i turn it on it just shows the apple logo for about 10 seconds then goes dark. it repeats this on a continuous cycle. Out of curiosity I reinstalled my cracked screen and it was fine, However when i install the new screen it still does the same thing time and again. Also my computer wont recognize the phone with the new screen. Update (08/08/2016) Turns out it was the camera ribbon cable that was faulty. To see if this is the problem, I unplugged it and booted the device as normal and it worked fine. Replaced the part and is good as new now
Probably a defective screen. Try contacting where you bought it from for a replacement.
