iPhone 5S shuts off unexpectedly
It's a 32GB iPhone 5S on iOS 10.2
This problem happened two times since last week. I've been on iOS 10.2 for months. When I try to turn it on by holding the sleep button, nothing happens (no plug in usb charger icon, nothing; just black screen). I tried doing a hard reset by holding the home and sleep buttons together and that worked. I'm worried that this will be a big problem later on.
Does anybody else have experience with this or know what I should do to prevent bigger problems down the road?
PS. The problem I describe is not unlike the problem they describe on the Dec. 19, 2016 osxdaily article titled "6s Unexpectedly Shuts Down? Apple Might Have a Fix!" But they don't really talk about the iPhone 5S there. Not sure if I'm allowed to post links so posted the title instead.
Edit: After hard resetting, 1st time the battery displayed ~75%, 2nd time the battery was ~82%.
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