Welcome to Android Central! Try booting into Safe Mode, which temporarily disables all 3rd party apps. On most Android devices, while powered on, press and hold Power until the Power Off menu appears. Press and hold the Power Off selection until the Safe Mode prompt appears. Tap OK.
If the problem persists in Safe Mode, then reboot normally and try installing a 3rd party keyboard, like Google Keyboard. If that doesn't work, then it's likely there's a problem with the touchscreen digitizer. If the phone is still under warranty, contact LG.
11-02-2015 12:16 PM