Idling issue

Hello,

One of the common causes for issues of this sort is a dirty throttle actuator.
When the heater gets turned on or other component that puts load to the engine, the ECM sends a signal for the actuator to increase air flow to the engine to counter the load by increasing the RPM. This prevents it from bogging down.
Dirty actuator might not get the signal or be able to adjust as needed.
So, cleaning out the actuator should be the first step, as that can improve the overall drivability as well.

Here is a helpful guide:

https://www.2carpros.com/articles/throttle-actuator-service

Is your check engine light illuminated? Sometimes with issues like this can trigger the engine light.
If it is on then a good step would be to scan and retrieve the fault code(s). This will help with the diagnostics.

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

I have attached diagrams for your reference.

Please let me know if you have any questions.
Thank you.