Soft Reset (Frozen / Unresponsive Screen) - Sony Xperia® Z3v
A soft reset can resolve issues like continuous resetting/rebooting, device crashing, freezing, device locking up, and keypad not responding.
This device has a non-removable battery. This process can be used to simulate a 'battery pull' when the device is unresponsive or frozen.
In most cases, a soft reset won't affect data on the device, unless the battery is very low.
Ensure the device isn't connected to a charger/USB cable.
Open the SIM card slot cover.
Using the tip of a pen or a similar object, press and hold down the Yellow OFF button (on the right side of the slot) until the device shuts down.
Do not use overly sharp objects that could damage the OFF button.