Why isn't my Samsung Galaxy S3 working?

[AC Question]

My S3 is more than a couple years old now, and it won't turn on. If I do get it turned on, it doesn't stay on. The problem was originally in my Nova Launcher app so I uninstalled it and the problem was fixed.... temporarily. Then it shut off again and after a long struggle of getting it back on it finally worked. It stayed working for an hour and the default launcher is unbearable so I switched to Hola. Which made my phone not work again... It's never on long enough for me to save my music and photos to my computer for me to do a factory reset..... I've tried safe mode, recovery mode, all of these things only work temporarily. Some of the problem might be coming from me using two batteries regularly (having a spare fully charged one handy for when the other one dies)?