If you mean the lines that you're actually drawing with your pen (upstrokes, downstrokes, etc.), you're not alone! I think a lot of us start off a bit (or, like me, a lot) shaky. For your first day, that is not unusual. So, ditto what Haley said about getting the muscle control down. Hopefully your paper is nice and smooth, because of what Sean mentioned, but really, you're likely to be a little wobbly on even the smoothest sheet on your first day (and beyond). Keep at it!
Edit: I should mention that your arm movement and how you're holding your pen will impact your steadiness over time.