2015 Nissan Rogue. About 20 seconds after we’ve stopped at a stop light the car engine seems to “shutter” a bit. It’s preceded by a click and lasts maybe a second. It doesn’t do this when the a/c is off but only when it’s on. The car drives fine and the a/c is fine but is this something that is a problem that needs to be addressed? Thanks.
Nissan has published a 5 page TSB # NTB15-048 (Technical Service Bulletin May 20, 2015) to help their technicians diagnose and remedy a shudder that could be what you’re describing.
2014-2015 ROGUE; VIBRATION IN STEERING WHEEL OR PASSENGER FRONT SEAT AT IDLE
They covered the diagnosis and repair for 12 months or 12,000 miles under warranty.
This could be your problem or it could be something else. I’m just putting it out here.
Perhaps somebody with a better PC set-up and more computer savvy could find or post a link to the text of this TSB so you can have a look.
CSA
Nissan does indicate that slight vibration and noise are normal under certain operating conditions (They aren’t in any of my cars, but I don’t own a Nissan.) 
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For owners bothered by it ( I would be one) then things to try are described in the TSB, but may or may not eliminate the bothersome noises and feelings. 
CSA