Was driving on 91 north 1/2 mile or so from exit 17A/B and something caught my eye in the sky. I looked up and saw a rectangular object with rounded ends; it was about the color of gun metal grey, leaning towards a brown color. It did not appear to move sideways to me, but might have been coming towards me. Approximately two seconds later the object "dipped" and the sun appeared to reflect off the object, turning the object bright white. The object looked different as it moved/dipped, going from a rectangular object to something trapezoidal. Almost immediately after this it disappeared, as if it "blinked" or was "switched" off.Direct answers to questions:1. I was driving back to work after picking up office supplies at Staples in West Springfield2. It was a very odd color and shape compared to other things I've seen in the sky3. At first I did not think anything of it (other than noticing its odd shape and color) until I noticed it wasn't really moving and when it then changed color (not really changing color but started to reflect the sun)4. Explained above5. During and after I became confounded as to what I saw; i still am shaking my head about it.