Android 6.0.1 keeps turning my WiFi off. :-(
This app can be configured to keep WiFi turned off, turned on, or leave it alone. Likewise with Bluetooth.
When first installed, it keeps WiFi on, but doesn't touch Bluetooth.
Important: this app may turn your Bluetooth on, or off, without prompting you for confirmation at the time.
It will only do so if you explicitly request the app to keep Bluetooth on or off. But once you configure the app to manage Bluetooth, it will do so, quietly, until the configuration is changed or the app is uninstalled. (Closing the app does not stop it managing Bluetooth.)
WiFi is similar, except that the initial configuration is to keep WiFi on.