Occasionally the van just won't start?

Occasionally the van just won't start. There are lights on the dashboard but not all of them are normal. For instance the mileage may be a funky mix of letters/numbers. Battery is goos, wires, good, all known electrical parts like wires, etc are good. No blown fuses. However, there has been gradual quirkiness with all things powered by the computer. Sometimes the mirrors move by themselves. Sometimes the overhead temp indicator goes blank. Door locks open and close by their own.
But back to the starting problem. If we tap on the aluminum looking module on the drivers side near the fender inside the engine compartment it starts and will be normal for a long time. Cold, damp weather seems to make it worse. One time tapping that module didn't work so I tapped the module on the fender on the passenger side inside the engine compartment and then it started!
Is it a problem with the one of the modules. Is it just moisture getting into the large cable connectors? Wht would tapping the module make it work. Loose wires. Why would tapping the other module work. They both can't be bad can they? If you don't know which modules I am talking about I can takes pictures.