Don't know how long you have had the S3, but you may need to wipe the cache partition, do the following:
1. Turn off the device.
2. Press and hold the Volume Up key, Home key, and Power key at the same time.
3. When the phone vibrates, let go of the buttons.
4. Press the Volume Down key to move to and highlight wipe cache partition.
5. Press the Power key to select and wipe the cache partition.
6. After the wipe is finished, go back up till reboot system now is highlighted and press the Power key to restart the phone.
1. Turn off the device.
2. Press and hold the Volume Up key, Home key, and Power key at the same time.
3. When the phone vibrates, let go of the buttons.
4. Press the Volume Down key to move to and highlight wipe cache partition.
5. Press the Power key to select and wipe the cache partition.
6. After the wipe is finished, go back up till reboot system now is highlighted and press the Power key to restart the phone.