In many cars, automatic engine shutdown is a feature that kicks in when the car is idling for too long. The thinking behind it is that if the engine is off, the car will use less fuel. It's a great idea in theory, but in practice, it can be annoying - especially if you're stuck in traffic and your car keeps shutting down on you!
There are two main types of automatic engine shutdown: timed and throttle based. Timed shutdown happens after a set amount of time - usually between 30 seconds and 2 minutes. Throttle based shutdown happens when the car's idle speed drops below a certain point - usually around 500rpm.
Both types of shutdown have their pros and cons. Timed shutdown is more predictable, but it can be triggered by something as simple as being stuck in traffic. Throttle based shutdown is less likely to happen when you're stopped in traffic, but it can be triggered by things like going downhill or having a heavy load in the car (like passengers or cargo).
The best way to avoid unwanted automatic engine shutoffs is to know what type your car has and how it works. That way, you can be prepared for it and avoid any frustrating situations!