The Situation Described here is For a Macbook Booting Without Any USB Device Plugged-In.
This Issue is Happened on my Macbook Air and I Found a Solution.
The Solution May?! Work only if you are Able & Intrepid to Open your Macbook…
But If you Are Not So Techy, you Do Not Want to Break the Warranty or Simply you Do Not Want to Take any Risks It Is Best to Bring the Macbook to an Apple Store :)
This Issue Can Manifest if your USB Connector Is Not Properly and Completely Plugged In! This Can Happen Because the Laptop is Exposed to Vibrations and Movements during Time.