If the following instructions will not get you out of "Safe Mode" then I would say there is probably something wrong with the Volume button on the phone, and until you fix it, there will be no way to get out of "Safe Mode".
To get out of Safe Mode, please try the following.
1. Touch and Hold the "Power" key.
2. Tap "Power Off".
3. Once the phone is off, Touch and Hold the "Power" key again to restart.
The phone should now be out of "Safe Mode".
If the "Safe Mode" is still running after you restart your phone, I would then check to make sure your "Volume Down" button is not stuck. Check to see if it has anything stuck in it as well, dust, etc. Anything like this can cause the phone to go into, and get stuck in, "Safe Mode".
If...