mine does this until it is warm, its the belt. I had a buildup of rubber on the pullys that just go for a ride, not the splined ones, it seemed to be the problem. A quick way to know is to run a bit of soap on the belt, even spit works and it should stop. On the soap just lightly touch the belt, too much may make it slip. They make a belt dressing but this is free. My belt went to 200k and then I replaced it, not too bad but a rad hose has to come off at the top (some don't but most I have seen do). My tensioner jumps and bounces until it warms the belt up. And chirps a little.
2003 7.3 Excursion Limited Ultimate, Mineral Grey Metalic. DVD, Limited Slip, Badged, Cab Lights, Magnaflow, Thule Rack, Top Gun Bumper, 3" Lift, T Prodigy, Air Bags, Edge Programer, XM Radio, Extreme sound system. PIAA Lights, Toyo 325/60/18s on Chrome Alum rims.