I have the same problem with my 03 Sorento I think it's the non-metal bar that
holds the door open. When I spray it with silicone it seems to help for a
while.

Hi David,  As you say, there could be the possibility of a slight
misalignment of the door latch, and the door latch striker? The door
itself may have slightly settled over time, and the striker in effect
now may be a bit high.  

This can sometimes be seen if observing very carefully when the door
slams, and latches, if the door appears to be raising at its closing
point ever so slightly.  Perhaps the use of masking tape will show this
more precisely.
Also look for any unusual rubbing at the latch striker.

Also make sure that the doors are even, and in line with the next door,
or quarter panel behind it.  If not, the striker needs to be adjusted
inwards a bit. (To do any striker adjustments, it is helpful to mask
around the striker in its original position with masking tape, this way
you can always return to the original position if need be.)

I would lube all door hinges with oil, and a light coat of grease on the
little plastic thingy by the hinges, which someone else has mentioned,
clean, and then treat all door weatherstrips with Amour All, and also
check all rubber hood stop bumpers for proper adjustment for height,
making sure that the hood is in proper height alignment with the fenders
(easy to do), and also give them a light coat with some grease.

The only other thing I can think of looking into, and checking for
rattles/noises, would be the sideview mirror.  Also, try this
experiment, but with the window fully lowered.
Hope this helps you,  Mark