Office max paper shredder switch

Question

Shredder works in reverse but not auto mode. I took apart the shredder and have full access to the switch. When first depressed the motor runs but only for a quick second and then stops (even though the switch is still depressed). You have to turn the unit off and on again (auto mode) to get it to work again but it's only for the one second, not continous. Any ideas?