This is a very good question. There are real physical conditions which could be causing this behavior, such as hyperthyroidism (over active thyroid). While normally seen in older cats, it can occur in younger cats. You need to have your cat thoroughly checked over by your vet.

However, sometimes this kind of behavior is caused through cats acting out their predatory instincts. This often happens at night and at the beginning of the day when cats are usually at their most active. You may just be missing the 3 or 4 hours that your cat actually does sleep.