How to Boot your Android Device Into Safe Mode using Volume Button
Step 1. Hold the Power button of your device. This will load the power options menu.
Step 2. Choose “Power off” from the options. Let your phone turn off completely.
Step 3. Turn on your phone. Press and hold the Power button again to turn on your cell phone.
Step 4. Immediately press and hold both the Volume Up and Volume Down buttons on your device.
Keep holding while the device boots. Once your Android device has booted, you will see the words “Safe mode” displayed at the bottom-left corner of your screen.