Chosen Solution
Hello, When I boot up my iPhone 5C, everything appears OK. I see the little white Apple logo. About 2 seconds after my home screen appears, the screen goes black. I have tried a new battery and a new screen, but the issue remains. I believe the phone is actually powered up. If I open iTunes, it waiting for me to enter my password.
Try doing a soft reset and see if that helps. If not, another battery might help. Definitely get new! It could be a software issue, so as long as everything is backed up, try a restore on the phone as well if the reset doesn’t work. Update (07/20/2016) Here is the guide to restoring without your passcode. Before you do though, when the screen goes black, plug in the phone and see if it vibrates. I would let it charge up for a while because it should automatically turn on if the battery was completely dead. If it does, try another screen.
