I had the same experience on my 1991 300zx one time. The whole "back" started to hop. I stopped and then tried to take off again, and the same thing happened. Then I put it into 2nd and took off fine.
My friend's explanation at the time was this. Depending on where you are in the rpm range, you power varies right? So at some "points" during your launch, you have enough power to overcome the static friction between your tires and ground and you peel out. Then I guess the revs raise so high, or drop so low(only experienced it once so I dunno) that you are out of the power band, therefore cannot peel out any longer and the tire regains traction. Then it comes back into power and repeats. This back and fourth action makes your tires grip, slip, grip, slip, ...etc.
Till this day, I still don't know if this is correct b/c that was back in high school, espcially how your revs moves when that happens. But from an engineering standpoint, it makes perfect sense.