My father has mild Alzheimer's and dementia. He stares off into space all the time.

It sounds like he may have Lewy Body Dementia instead of Alzheimer's. Have a movement disorder neurologist look at him. With LBD they have no facial expression, seldom talk, and shuffle slowly when walking. It is important to find out because medication for dementia can be very wrong for LBD patients.

The vacant look and the walking are part of the disease. Enjoy the times he is more alert.

Your father sounds restless, Lisa; perhaps anxious. But you are more disturbed by that blank, spaced-out look, aren't you. It's a feeling of vacancy and not being able to communicate with him.