My Mavic Air initiated auto-landing in light fog several times during a flight. This was harrowing as the drone was pretty far away. I’ve never had this occur with my Mavic Pro, so I reckon it was in fact the Air’s sensors.
Wild parakeets ('maritacas') have aggressively swarmed my drone several times in Brazil; they attack in screeching, fast-flying squadrons of a dozen or two. They get really close, and I've always landed immediately without further incident, so I don't know if they'd actually strike the drone...
I've been wondering about this too.
It'd startup, and recover -if it's high enough. As a reader above mentioned, people have done mid-air power-offs followed by free-fall restarts, which is basically the same thing.
Check that your phone is actually connected to the controller, it can be plugged in yet not have a closed circuit -push the connectors in.
Also, check that the Mavic's switch is solidly to the right, to "RC".
I've had both problems, several times.