Why does my LG G4 keep restarting with a significantly lower battery?

Hi, for a week or so my phone has started randomly restarting and then when it comes back on after a few seconds the battery has dropped significantly. For example it will be on 50% and then it'll come back on at 3%. I think the phone reboots more when I go on the camera app. I also keep getting a notification saying something like "the Android media processor has stopped working". It is really annoying obviously as it just turns off to turn back on with a super low batter life!? I am very out of warranty so any help of what I can do myself is appreciated!
Thank you!

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