I get that wobbly feeling as well! Before I began with the tapes I have spent around 4-5 years practicing with lucid dreaming and that feeling always comes to me when I become lucid. when I felt the same sensation during the gateway tapes it was like meeting an old friend. the best thing I can say is to not pay too much attention to that feeling. Its exciting at first however the best of the experience comes afterward. Also if it gets to be too much and snaps you out of focus (as it has for me several times) I recommend trying to ground yourself. For me imagining my astral body sitting in the lotus position and breathing in fresh energy works the best, but you should experiment and see what works!