Need some help
 

I notice a vibration in the car today, it seems like the rpms are dipping down while its in idle (park). Remind you, I'm in the front passenger seat and I feel the vibration below my left foot. Is it something I should worried about ? I'm due an oil change soon, you think once I get my oil change, it would fix the problem, or should I bring it in to the dealer to figure out why it feels like its vibrating. Let me know what you think. Also, the car seem quiet on the outside, but whenever I drive the car, I don't feel the vibration of the car, just whenever I'm in a full stop for a few minutes or the car is parked.

Sorry for the long essay, any suggestions would help.

Mine does something similar. Every once in a while with the A/C on and on a relatively warm day the car will seem to shudder for a second or two when stopped (like at a light). The RPM's do drop a bit when this happens and when I first took notice I thought the engine might die but it never has. I think this might be the A/C compressor but I'm not sure. I have just kinda gotten use to it. Hasn't cause any problems.

Also my max does the same as well

I used my AC too, and it happens to me, but I think that's normal. But I don't think in a full stop, that I would feel a vibration, or whenever I'm parked. Anyone think that a car needs a tune up already ? I really doubt it though !