Every time I take a video at night with my iPhone Air, it seems like there's a light reflection.

My next door neighbor, who is a professional landscape photographer regularly using $10,000+ cameras and lenses has the same problem that you do. It's called lens flare.

He has to experiment by angling the camera. Even then, sometimes that won't work all that well.

Some interesting info in this other thread:

Lens Flare and Reflection Artifacts Appe… - Apple Community

Yes, same with any camera shooting sharp bright lights in dark conditions. Angle your camera to avoid it or patch them in a photo edit app.