My iPhone SE on iOS 12 has been acting strange recently.
Yesterday, it turned off at around 10% and when I tried to turn it on it said that it has no power. Two minutes later, it turned on and said it had 14% capacity remaining.
Today, when it was at around 10%, it turned off. Then I turned it on and it said 12%. Two minutes later, it turned off. It says "connect to power."
After a few minutes I tried again and it turned on. Then it gives an error saying that it "can’t connect to my mobile data network" and then the phone crashes.
I turned it on again, and it worked normally.
What is causing this?
EDIT: After digging around my batter settings I found this: