After reading some of the follow throughs, it's almost sounding like and electrical connection - like a ground(s) issue. For reasons:
a) wet weather - problem didn't seem to be present
b) when cold - problem wasn't as evident.
In both situations mentioned, cold or wet contact seems to be better. When warm electrical contact(s) expand. Start looking for coroded contacts on all electrical connections (green or exposed) Get yourself a small wire brush and start cleaning connections. Especially if car has such low mileage and has been sitting - I suspect you'll find your problem.