Sleep walking completely freaks me out! What is going on in the brain?

Unusual chemistry. I would be willing to bet that you have many other symptoms because sleep walking, talking, eating are all related to defective chemistry in the lower part of the brain that initiates autmaticiity. The easy way to produce it is high calorie malnutrition. Get rid of the empty calories, paraticularly all forms of sugar and sweeteners. See my blog "oxygen the spark of life" that you can google.