I have seen issues like this related to the IAC Intake Air Controller.
The engine requires an unrestricted amount of air to start. For this the EEC opens the IAB 100%.
As soon as the engine RPM self sustains and begins to stabilize we now need air to Idle
On my '98 V-6, its mounted on the top/side of the throttle body. Air is allowed in from in front of the closed throttle body, and “bypasses” the throttle body plate. The air is then released into the open intake track flowing directly to the cylinders. The whole idea behind this is simply a way for the computer to give air to the engine without needing a driver. The IAB is either open or closed completely.
I have experienced when carbon builds up inside it prevents the little plunger from opening or closing. So I took it off and cleaned the mechanical area (not electrical) with some air intake cleaner and a Q-tip.
Manufacturers suggest replacing for $60 to $90, but my way worked and was cheaper.