It is hard to guess without being able to experience the problem first hand your car's computer controls the idle speed electronically. I wonder if there is a problem with the idle speed control system or some other under lying problem. Your car has on board diagnostics level 2 (OBD2) a 16 pin socket under the dash allows the computer in your car to be interrogated using a scan tool to read live sensor data that may point to the problem with out having to do extensive testing at each sensor. Interpreting all the sensor data can determine if a particular sensor is failing, the engine is mis firing, running to lean ect..... Plugging in a professional grade scan tool is often the cheapest and most efficient way to find drivability problems. High end automotive scan tools (like dealerships and independent repair shops that specialize in Dodge ) have by directional control, the scan tool an "drive the idle speed high or low to see if the control system is functioning correctly.