usually the switch is just coated with dust and stuck.....once you get to it...you can clean it up good, and blow it out with compressed air, and return it into service for another 3-4 years.
Typically the drivers door is the one that acts up the most, because it is the most heavily used....but if you can kind of figure out when it happens by which door you just opened and closed that will help you out, cause sometimes it isn't the drivers!