The Nissan Path

Hey guys, I was wondering if anyone could assist me with an issue I just started getting with my 06' Pathfinder SE. When the truck has been sitting in the driveway for about 12 or so hours and I go to start it I get a HORRIBLE noise when it first cranks over like something is flapping/grinding/and sucking for about 5 seconds, then goes away and everything is fine. Engine mellows right out and runs fine, gauges all show fine and I have already had it to a shop who could not get it to make the sound but checked it over and didn't see any glaring issues.... I actually took a video of the noise. Here is a link to it on YouTube: http://youtu.be/nxFIKsPc1t0

weird

checked the radiator shroud or any loose plastics near the fan?

The inconsistent frequency of the sound makes me also think it is something related to the fan shroud. Odd that it only does it after sitting for a few hours. Maybe a bad fan clutch? You got me stumped.