Since I drive older cars, I did not know about this:

Stop & Start Technology automatically stops and starts your vehicle’s engine in certain situations to improve fuel efficiency & reduce greenhouse gas emissions.

Source: Automatic Stop & Start Technology | Vehicle Support | Chevy

A number of 2016 model year cars and newer have this feature. However, due to the semiconductor shortage, some makers discontinued the feature in 2021.

For those driving in city traffic with frequent stops, this feature can reduce gas consumption – one article said by an average of -12%.