i had the same problem,change ur battery it will fix it till that battery fucks up too.I always bought iphone because android use to be so shit,now android os works fine and there are so many good android phones,never gonna buy this overpriced shit phone again.
change your default shitty battery for a real one
ever heard of lithium batteries?
My phone does the same when it's cold enough outside.
Same because my battery is old and shit