Hello, I'm an end user as well.
I have a similar issue where the shadows of tree branches on the ground makes the camera think it is seeing people. If you read thru this forum you will see a number of people reporting this kind of false alerts. Sadly, I have done a lot of looking and this is a problem on most of these home security cameras. It is not just restricted go Google Nest.
Your best bet is try and reposition the camera to a place where it can't see the cars.
Sorry I wish I had a better answer.
