[shorod]

Does the needle just drift slowly or does it jump? Also, check the battery connections and make sure they are clean and tight.

You also may want to have the battery load tested. A weak battery can cause all kinds of strange issues on modern cars. At idle, the alternator output is low. You may want to try putting the car in park and taking your foot off the brake pedal sometime when it acts up and see what happens. If the drifting stops, then I would definitely suspect a charging system issue. If not, try revving the engine a bit and see if that has an effect. A weak battery/charging system would help explain the roughness that you think you've experienced a couple of times.

If you can in no way tie the battery or charging system to the issue, then you may have a grounding problem in the instrument cluster, but I would expect that to cause the needle to jump rather than drift.

-Rod