This could be a few different things. What I would start with is simply checking for engine vacuum leaks. If there is one, it can cause what you described.
Here is a link that shows how it's done:
If no leaks are found, then suspect it may be carbon deposits on the throttle body or the IAC (idle air control valve). The IAC is responsible for maintaining idle speed.
Here is a link that explains how to service the throttle body:
Next, here is a link that explains how to service the IAC:
I attached a pic below showing the location of the IAC. It is mounted on the throttle body.
Let me know what you find or if you have other questions.
See pic below.
Saturday, August 28th, 2021 AT 11:03 PM