It's a speck of dirt stuck on the car windscreen that appears to catch up with the image of the meteor in the line of sight of the camera, then moves away again as the angle of the flight path of the meteorite relative to the camera changes due to the car changing direction to follow the meteor trail. The change in direction of the sunlight hitting the windscreen causes the speck (which was dark because it was momentarily blocking the sun's light) to vanish because some of the light reflected off the windscreen glass instead of passing through it.