The fueling system on these cars a is a little dated. Most of it is mechanical and if it isn't used it can start to get a little tight. Chances are that using the car is freeing everything up again and making it easier to start.

Mine ran like a sack of shit after not being used for 3.5 years until it had run for a bit. I still don't like the way it runs so the KE-Jetronic is coming off eventually and new engine management is going to be fitted.