
Could be a transferred reaction to an activity or sound that no longer occurrs? Our Lab never bothered with the electric drill till the OH was doing some bathroom renovations and had to drill through cement board. That made the most horrible, high pitched, squealing, fingernails on a blackboard kind of sound and the smell was awful too. Now the dog reacts to drilling on any surface and using the drill to put in screws. Shaking, just as you say, but she will also try to climb up on my lap. We can even tell when the neighbours are using their drills. It wan't hard for us to isolate the cause of her stress. We did not try much to correct her, I just use it as an excuse to sit with her and read a book or watch TV. Playing cover up sounds, like the TV or a CD, doesn't help much in our case but might be worth a try, if it is a sound in your case.