Is my Nikon SB600 Speedlight broken? (VIDEO PROVIDED)?

When attached to my camera, it doesn't respond to my settings. When I attempt to alter the settings or turn the flash off, the screen turns completely blank and returns to normal shortly after.

I've provided a video that shows my attempts to alter the settings. I'm not sure if my batteries are too slow/messed up, if my flash settings have been changed in some way or if it is just broken. I'm not experienced with this flash so I'm not 100% sure on its functions.

Have you changed the batteries? Looks like a low battery problem. If that doesn't help you may want to seek professional help.

Be sure batteries are fully charged or new. Weak batteries can make the controls respond in strange ways. Also, be sure the battery contacts are clean and no corrosion products are on the contacts.

Next, reset the flash by pressing the mode and power button for more than 2 seconds. See page 13 in your flash manual. See if that does something to get your flash working.

If the above two things don't work, your flash may need repair.