Recently, I removed the SIM card and will use the phone for Wi-Fi access only. But Wi-Fi keeps turning itself off without warning! The issue is resolved by entering settings and re-enabling Wi-Fi.
The problem is repeatable: The phone remains connected for some time, and can be used without issue. Some time later after stopping use, Wi-Fi will have become disabled. I am unsure how long after stopping use before Wi-Fi is disabled. My estimate is around 60 minutes, but it could be variable.
How do I stop Wi-Fi from disabling itself?
If relevant, running Android 7.1.1.