I was alerted to it by the Sun's refection & lack of movement.

I was sitting in a chair, relaxing. A light shining in my eyes caught my attention. I looked up & several thousand feet above my head, was a multi sided, silver object rotating slowly back & forth. Each time one of the crafts sides was in the correct position, the sun reflected brightly into my eyes. I continued watching for 30 seconds & this activity continued. The craft was stationary. Zero movement but the rotating back & forth slowly. Zero noise. Zero smoke. Zero flame. Zero wings or propellers. Suddenly, it vanished. The craft did not fly away. It simply vanished.