Iphone 5s repeatedly crashes about once every minute of use

I'm currently using an Iphone 5s with the 11.0.1 IOS. Just today, out of the blue, it started crashing when I tried opening any app. By "crashing", I mean that the screen blacks out completely and shows a white loading circle before showing the lock screen. What is the cause of this issue and how do I solve it? I've seen a post online stating that downloading the latest IOS might solve any issues. The problem is, my phone crashes in the middle of the downloading. Even though the phone is still downloading the latest IOS when it starts up again, eventually, it will show an error message that states that I'm unable to download the update, even though it's clearly shown under the storage settings, and takes up space.