Why do I blank stare at times?

Maybe. Depending on the degree of distractibility, an adhd person could stare off. They themselves call it "zoning out." if a stare occurs during a voluntary activity such as speech, eating, driving, etc, then it could be petit mal or absence seizures. Think of charlie brown's teacher's "wah-wah-wah" sound turnig off an inattentive charlie. Best to check those symptoms out with your doctor.