The ancient Buddhists were quite familiar with the tendency of restlessness to interfere with meditation habits, but we moderns have more opportunity for distraction than perhaps any other generation. Such restlessness can seriously interfere with your meditation regimen and make it hard to sit still amidst the various stimuli fighting for our attention. Even in the relative absence of abundant stimuli, however, it can be tempting to want to get up and move around for a bit, or even just sit there and move around, either back and forth or left to right.
Indeed, the mind itself tends to be inherently restless. This makes certain temptations much more appealing to us, and we begin to fabricate (oftentimes convincing or reasonable) excuses to stop meditating. Our method with dealing with restlessness is similar to how we deal with anything else we encounter during meditation, positive, negative or neutral: We acknowledge its existence and allow ourselves to understand its source. Notice how it feels without judging the restlessness negatively or attempting to fight it and it will gradually evaporate.