When I read your post, I remembered that after the ms updates install there is a timer that counts down and restarts the computer. I thought it was strange because mine, win7, waits for me to tell it to restart. We were also having problems with ms automatically downloading & installing in the background. I have reset it to notify when downloads are available, but every so often it reverts back.
"Whenever they invent something that's moron proof, someone comes by and invents a better moron."
"Ever stop to think, and forget to start again?"
"Those of you who think you know everything are annoying those of us who do."