1990 Ford Festiva LX Hatchback 2-Door 1.3L

This is a one-owner vehicle with various mechanical/cosmetic problems typical for a 25 y. o. car. The original engine was replaced 10+ years ago. The car normally starts & runs well. though it does burn/leak oil. It has recently shown intermittent starting difficulty. typically after not being driven for several days and sometimes immediately after fueling(?). Mechanics have been unable to diagnose problem. as it always starts and runs perfectly when at the shop. The car still gets 40+/- MPG. We hate to give this car up. but it is just no longer dependable for wife's job as a home health nurse.