Shutting off at stop signs

Sounds like it is time to clean the throttle body and check for vacuum leaks. The first item is because it is the job of the throttle body to maintain idle speed and they get dirty and the deposits will block air. Once the engine warms up the deposits can "soften" and let the parts move better and the idle control returns. The search for vacuum leaks is because you can actually have a vacuum leak while the engine is cold and once the various parts heat up and expand the leak goes away or gets much smaller.

Not your vehicle but it gives a general idea of what is involved with cleaning the throttle body. https://www.2carpros.com/articles/throttle-actuator-service