I have a personal one with my car: if from a cold start during spring/autumn temperatures (or early mornings in summer), I drive about a km and shut it off, then come back to the car after a few minutes it will not manage to stay idling once I turn it on. What happens instead is that the RPM goes too low, and the engine shuts off, then the start/stop feature kicks in and restarts the engine. This happens every few seconds repeatedly. If I press the accelerator it can keep running. And if I just drive a meter or two it will work fine again when I go back to idling.

I tried both with neutral or in gear but with the clutch pressed (yes, it is a manual, fairly common in Sweden still) and that doesn't make a difference.

I haven't managed to figure out the cause, but since it is a modern car I would assume it is something with the ECU that goes wrong. (It is a Dacia Duster in case anyone else recognise this issue. The mechanic I asked hadn't heard about anyone else having this issue though.)