I know that sometimes things like the MAF or what not will not be working properly. But not throw a code. Had that problem on my old truck. When it was cold and in gear it would occasionally idle low and vibrate bad. Or it would start to "hunt" the tach, where it would drop really low then up, then low, then up. A cleaning of the MAF and throttle body sorted that out. I'm thinking you might have a similar condition where the MAF (or other sensor maybe) isn't sending right and when you put load on the engine when cold, it doesn't appropriately raise RPM, either by adjusting fuel or air intake, to compensate and stalls out.
IF that makes sense.