I was having this same issue with my old Samsung Galaxy S3 (which I still keep to take on vacation to the West Coast every summer to take pictures).
After Googling possible answers, I was resigned to having to reset my device. I decided to try one last time to remove the battery, and took off the Otterbox Defender case. Once the case was off, my device miraculously started normally! I am wondering if the tightness or fit of the case might have had something to do with the issue.
I did make sure to back up all of my photos, just in case this happens again. Just something you might consider. . .