I think Mike is on to something. I've read here on the board that these bursts of hot and cold air could be due to a malfunctioning monovalve.
If you're lucky, your 103 engine has a repair "kit" that you can buy instead of a whole new monovalve. The later 103's don't have this luxury.
'01 E430, Sport 72,000 mi
'98 C280, 126,500 mi