Assuming no odd mods I'd check the closed throttle position switch. That switch has continuity when the throttle is fully closed and tells the ECU that it must take over and control the idle RPM via the Idle Speed Control (ISC) valve. If the switch or the idle position set screw is misadjusted so the ECU doesn't get the word, you will get exactly what you've got.

Another possibility is the ISC valve itself. If stuck closed ...

There can be other things but those are frequent offenders and not hard to check.

Adjust your idle screw out.

is this car stock?