Assuming you're using the Valhalla (or earlier) power supply, then you should definitely use some way of hard-switching the mains connection off when you're not using the table. The transfomerless design results in constant active and heated components on the board even when the motor isn't engaged, which at best lowers the lifespan of the supply.
(I can't speak to the spontaneous power up you're seeing, but that could be something borderline or failing in the circuit.)
(I can't speak to the spontaneous power up you're seeing, but that could be something borderline or failing in the circuit.)