LG K4™ - Soft Reset (Frozen / Unresponsive Screen)
View this info if your device is unresponsive, frozen or won't power on or off.
Turning the device off and on is sometimes called a soft reset. This is similar to restarting a desktop computer and is often one of the first steps in troubleshooting a device. In most cases, a soft reset won't affect data on the device unless the battery is very low.
Simultaneously press and hold the Power and Volume down buttons for 12 seconds or until the device power cycles.