First and foremost, a diagnosis can only be given by a medical professional. Based on the limited information available, it doesn't sound like anything you should obsess over. If, however, you have other symptoms such as mood swings, occasional depression, or variations in energy level (more than what is considered normal) you might be looking at something like Bipolar Disorder.

Webmd has a good list of Bipolar symptoms which I cannot link to you at this time due to my post count. If they seem uncannily familiar, you might want to look into speaking with your doctor.