electronic 4 wheel drive enegages itself

My 2001 S-10 will occasionally put itself in 4 wheel. It's happened when I just startup in the morning, while idleing in neutral at a drive up window, and while sitting in park. My dealer suggested that perhaps I was bumping the button when shifting but I really don't believe that's what is doing it. They checked the module and couldn't find anything wrong.
Anyone else have this problem? :banghead: