Is it normal that when first started the fan clutch is engaged for about 15 seconds with noticeable noise then it quiets down , sounds like the clutch is engaged, then it disengages and all is quiet and normal running engine noise ??
I believe this is a viscous clutch and yes the fan clutch can make a loud noise when started from cold.
Most fan clutches allow the fluid to drain into the working area when shut down
and this will engage the clutch. At starts it may take 1-2 minutes for the clutch to quieten as it slows down.
Here's a good link for information on viscous fan clutches ; Fan Clutches