Make sure that the orientation of the cord is not applying force to the main body of the mouse. It's such a light mouse that this can definitely cause the mouse to physically move.
Ok, so I noticed this the other day as well. This happens rather rarely for me (typically when laying the mouse back down, effect disappears as soon as I move the mouse again). I've only opened the mouse to take out the weight, never took a look at the sensor. One thing I've read about is there seems to be alot of refurbished g100s' labeled as brand new going around (not sure how true this is). I have another g100s on the way which is suppose to be certified brand new (according to Amazon). Will see if that mouse has the same problem.
It seems my issue was mouse pad related. Cursor would jitter about on its own (mouse being perfectly still with no pressure exerted by cord or otherwise) on my Goliathus Speed and Icemat equivalent (not much of a surprise on that one I suppose). This would happen if the mouse was lifted only slightly (less then half way to its LOD on the Goliathus and a quarter or less of its LOD on the glass pad). Was unable to reproduce the effect regardless of mouse height on my Shinden Kai so I'm sticking with that now. Another thing to note is if you use anything thicker than the stock feet (I'm using modified hyper glides myself) the effect will be easier to reproduce on said mouse pads.
Artisan Shiden Kai (Mid) is my favorite atm as I prefer my pads to be as fast as possible. The g100s also seemed to work perfectly on my Allsop Raindrop XL. I might have a few other pads I can try out but that will have to wait for tomorrow.