I don't know what's wrong with my IPhone 5C
If you want to reset your iPhone, maybe first you should backup your data. You can try to backup your data on iCloud, and then restore your iPhone. Unfortunately, you said that you can not back up every time, can you connect it with your PC? If you still can't backup data, you can try to restore your iPhone 5c directly and see how it goes. Don't be afraid. Good luck.