No make and model, no detailed answer. What kind of woofer is it? What is it used with?
If you have a self powered subwoofer with auto turn on then that circuit in the sub could be bad. If there is a switch to leave it on then set it that way. It won't pull much electricity without an input. If not then it would have to be repaired.
If you have a another kind of woofer the answer might be different. Bad amplifier. Bad AC outlet.