Volvo: Warm ups and noise, temp gauge, warm ups

Question
I have two questions about my 1995 850. 1) Is it necessary or advisable to warm the car when first starting it up and before driving? With the cold weather we have been having, I try to keep my speed below 40 but it can take 5 minutes or so before the temp gauge moves up to the middle area. I don't idle it, but just keep it under 40-45. 2) My 850 has 95,000 miles. I notice a slight "hum" or "twangy rattle" when I accelerate after having stopped at a traffic light (not every  time  but often). It sounds like it is coming from inside the car in the area of the dash. It lasts for a second or two and then goes away.  Could it be the fan? Or just a sign of age? Do I need to bring it in?  

Answer
Zach,
Really no need to warm up longer than a couple of minutes.
That humming sound would be something that you would have to hear and then follow the sound. Have only found that noise coming from the small fan that is part of the climate assembly, and that is mounted by the grab handle top of the door, on cars that have the ECC climate system.