B757-200
Flight Crew Instrument; Flight Crew Air Transport Pilot (ATP); Flight Crew Multiengine
Communication Breakdown; Confusion
Deviation / Discrepancy - Procedural Published Material / Policy; Ground Event / Encounter Other / Unknown
Flight Crew Became Reoriented
Human Factors; Procedure
After engine start and after start check Captain released brakes and began to taxi before [technician] disconnected and cleared the aircraft. It was the first time to ZZZ for both of us and the aircraft was already in position to taxi - there was no push back. Additionally we had a wheels up time that was 8 minutes from the event. Capt. had me call for taxi and as I was reading back the taxi clearance and looking at the airfield diagram we began to move. [Technician] called out 'stop; stop; stop' immediately and Captain stopped and set parking brake. Estimate airplane moved 2-3 feet. [Technician] disconnected and departure was normal after.As a pilot monitoring I could have anticipated possible issues with operating in a new place and new scenario. Simply mentioning 'I guess no push back' may have planted the seed.Being more methodical in a new/strange field/situation. This is especially important as more distractions are added in. Non-[Company] personnel could also be more standardized as far as verbalizing the checks that we get at all the [Company] ramps and hubs.
[Report narrative contained no additional information.]
B757 flight crew reported beginning to taxi while ground personnel still had a headset connected to the aircraft.