I have a one year old iPhone 5s. After about six months of use it started crashing and restarting. This often happens when launching an app, when I imagine power consumption may be at its highest. Through trial and error I noticed that enabling low power mode prevents crashes entirely. Without low power mode I get about one crash per few hours. I have tried wiping the OS and reinstalling to no avail.
What's happening and what can I do to fix the problem?
In case it's relevant I will describe what I see during the crash and reboot. The normal Apple white startup logo appears on a black screen and occasionally when it crashes there are thin vertical red and blue lines.