Way 1: Hard restart your iPhone
1. Keep pressing both the “Home” and the “Power” button until the Apple logo comes back on again.
2. Then release both buttons and your iPhone should boot up successfully.
Way 2: Use ReiBoot
1. Download the totally free Reiboot Software on your mac.
2. Connect your iPhone to PC and launch the free iPhone reboot tool. Reiboot will detect the condition of your iPhone automatically.
3. Click "Enter Recovery Mode", "Exit Recovery Mode" or use both according to the detecting result to reboot your iPhone.
Way 3: Restore your iPhone to factory settings
1. Connect your iPhone (make sure that it is in the Recovery mode) to PC and select your iPhone when it appears on iTunes. Click "Restore iPhone".
2. Click "Restore", confirm that you want to restore your iPhone.
3. Then iTunes would display the latest update information for you, just follow the wizard and iTunes will automatically download the latest firmware used to update iPhone to iOS 9.
4. When finished, you'll see the Hello screen. And then you can select" Set up as “New iPhone" or "Restore from iCloud/iTunes Backup".
Good luck! Hope can help you! As an iPhone user, we may often lost data from iPhone, I often like to use iPhone data recovery to recover my lost data, and you?