I always feel the need to be doing something both physically and mentally, is this a disorder?

Maybe: Any number of neuropsychiatric conditions have restlessness or overactivity as symptoms. It's best to discuss this with your doctor. Btw if you're using stimulants to excess, restlessness could result (if it's a new thing). If you've had this all your life, it could be attention deficit/hyperactivity disorder, bipolar disorder, or ocd. How much it impacts your life is important to consider.

Restlessness : It could be. For example, it may be a manifestation of adhd, which is characterized by attention difficulty, restlessness or hyperactivity, and acting in highly impulsive ways. But it could also be related manifestations of bipolar disorder. If your restlessness is of concern to you or to someone who knows you well, consult with a psychiatrist or psychologist about it.