This strongly suggests that the swirl flaps are causing the vehicle to enter limp mode. During the first startup, the swirl flap actuator does a sweep to assess the range of motion. If it identifies a deviation from specifications, it activates limp mode, but the engine management light may not illuminate. The vehicle performs the sweep just at the first startup; so, when it is subsequently turned off and restarted, the engine reverts to full power mode. Scanning it should reveal the error related to swirl flap deviation.
Thank you.