This morning when i first drove the car, (it was about 19 degrees F out), there was a noise from around the passenger glove box. It sounded like it was a cell phone vibrating in there. This wasn't the case, but I am curious to know what was kicking in. Is it some sort of pump? It went away after a while.
And it wasn't a fan which goes on sometimes when I start the car, that has a completely different sound.

 

Next time it happens turn the heater off and open the hood and see if you can pinpoint where it is coming from.

 

Your heater blower is behind the passenger side of the dash. Could be the blower protesting the cold. Do like Spike said and turn off the heater next time you hear it. If the sound stops when the heater is off then I would say that's your problem.

 

Thanks. Will do in the morning. If it is the heater blower is that normal until the vehicle heats up?