Why would '92 Buick Park Ave not start for several hours after being shut off?

I am not sure of the answer but we are having the same problem with a 1991 Park Avenue. The alternator is a year old and the battery is brand new. At this point, I suspect the selenoid but no confirmation. Also I have noticed a problem with moisture build up. THis could somehow be affecting the electrical system. The car is not driven that much.