A short film known as Spin, made in 2004.
It’s about a physicist who is bicycling down a hill and a car is in his path. The driver turns to see him and hits his brakes in the last moment. He skids over the hood, mostly unharmed and begins to ponder this.
If the driver hadn’t had the single neuron in his brain fire and trigger him to look again, he wouldn’t have hit his brakes and he would have collided with the flat side of the car, likely killing him.
He applies this idea to quantum physics and realizes that this is happening with every decision made by any living creature at every waking moment, creating countless split possibilities for all moments in time.
The final scene is very striking, showing a car approach an intersection. The view splits to show the car turning both left and right. The camera splits multiple more times to show the concept that you can always choose any path at any moment. Some are just more likely than others.
It showed on IFC back in 2005 or so, and I’ve tracked down some limited information on it, but it was shot on 35mm and I’ve found no real leads on watching it anywhere.
This is the very limited IMDB page for it.