Is it in your lap when it moves? If so then normal
moves on its own on a flat solid surface? not normal
As per Apple.com, the video above doesnt fall within this parameter:
Learn what you can do if you experience one or more of these issues with the hinges on your MacBook Air.
- Unable to close lid completely.
- Broken or cracked plastic near one or both of the hinges.
- More than one inch (2.54cm) of free play while opening or closing the lid.
- Lid falls freely into closed position from a 30-degree open position. (From a closed position, open the lid approximately 30 degrees and let go.)
END from Apple.com
The hinge in the macbook AIR hinge, a friction hinge.
Due to the thin nature of the LCD backlit LED monitor on the Air, you would NOT WANT a very tight hinge.
Why? Excessive hinge resistance would cause the screen to BOW (and possibly crack), especially on a longer fulcrum from the hinge in the case of the 13" screen...... Ergo it is designed logically to be “looser than” a traditional macbook Pro's hinges for a very good reason.
Friction Hinge: A device with torque between two parts on a common axis.
A friction hinge is also commonly known as a:
Constant Torque Hinge, Position Hinge, Clutch, Torque Hinge, or Detent Hinge.
Common Applications include:
Laptop computers; lids, doors and enclosures; positioning device for controls, monitors, arms, seat rests
Contact Apple for in shop diagnostic 😊
Ive owned 3 Airs, some of the friction hinges are a hair tighter than others, but nearly all (never seen one that wouldnt) WILL IF you lift them up when at a 90 degree angle, ....if you lift up quickly, or tilt it back a bit,...the screen will flop open.
Friction hinge in the AIR see pic below (there are NO SPRINGS in these kind of hinges)