New video in the motorcycle/Ian Ziering wild fight shows the "Beverly Hills, 90210" star is the first one to throw a punch that triggered an all-out brawl.

The video is shot from behind. You see Ian's Mercedes stopped on Hollywood Blvd. -- the car in front of him had stopped and blocked his path forward.

Members of the 605 Minibike Gang roll up behind Ian's car, with 2 of them stopping right in front of the vehicle. It seems as if they were trying to block him from moving. At that point, there is no physical contact between the bikers and Ian, or the motorcycle and the Mercedes.

Ian lunges out of the car and immediately shoves one of the bikers, which then sets off the brawl.

The mystery ... Why was Ian at a 10 when he stepped out of his car? It would seem something happened between Ian and the gang before the video starts rolling.

Ian broke his silence on Instagram saying he was "unscathed" with his daughter after the incident -- and called on L.A. officials to take action against what he describes as "hooliganism." We have repeatedly tried contacting him, to no avail.

We did get photos of Ian at a WeHo supermarket wearing a hat with the words "Good Vibes" emblazoned on it.

As we reported, the LAPD is conducting a felony vandalism/misdemeanor assault investigation.

Stay tuned ...