How to find out what is causing hang My phone (Huawei P8) is hanging. It is hanging when it's not "in use" (at least, not by me or anyone else).

When it hangs, I have to hold down the power button for 10 seconds. When it restarts it works fine. I can single press the power button to put it to standby and return from this state as expected.

I then leave the phone for an amount of time (10 minutes, 30 minutes... whatever it is) and when I return, it has hung.

It still shows the lock screen when I single press the power button.

How can I find out which app(s) or hardware is causing the issue?
Keep using the device as there is a good chance you'll see a notification that a given app has stopped responding. This will then give you the opportunity to configure/update/uninstall etc