There is an automatic climate control fan right above the button to active seat heating. The fan grate looks like a target. When this small fan gets dust or dirt inside around the fan bearing it will start to buzz since the fan isn't balanced.
If you get a can of air (like keyboard cleaner), and blow it into the fan, it may clean it out. If this doesn't worky, use a flat object to pop the fan out and blow it from the other side.