Altair

Hello everyone, I'm new so I hope I am posting this in the correct section. I have a new (new as of December) 2006 Scion xB. The question is that in the cold weather when you turn the engine on and the heater turns on and for a few seconds the windshield fogs up, I can see at least 4 perfect cirlces on the windshield perfectly spaced apart close to the middle. There may or may not be more, it is hard to see them as they only appear for a couple seconds. I was wondering if anyone knows what these could be? Theres nothing that would have been placed on the windsheild (its much too steep anyway). They are ~3 inches in diameter. The only theory I have is that it is the suction cups used in the factory to move it into place. I know this is a pretty odd question but I am just curious and was hoping someone might have some insight. Thanks, -altair