Would you believe the original is by Gary Glitter? I had not known that and, frankly, preferred not knowing. But anyway, Joan's asking the question like she doesn't already know the answer. Do you wanna touch her there? Hells yeah, you do! (I'm guessing.)
OK, so officially (according to the band) the song's simply about being pumped up for a night out on the town and "jerking it out" refers to letting all that energy loose while dancing and just generally having a good time with your pals and whatnot. Some fans assert it's about self-pleasuring. In either event, I like to think that the singer's got his girlie nearby, ready to lend a hand. As it were.