Had this issue just before on Windows 7 64bit however my mouse moved to the right not the left, was concerning when it happened as it's a Razer Naga mmo expert mouse (with a 4G laser) not some cheap one.
First thing I did was clean out the bottom of the mouse and no luck then I grabbed my old mouse and tried that one and the pointer continued to do the exact same thing (move slowly to the right every now and then) so I then restarted the computer and well the mouse no longer moved on it's own however I found the sensitivity of the mouse was off like it had been cut in half so went into razer synapse and increased the DPI to the max at 8200 up from the normal DPI of 4600 and still felt a little slow (and weird normally at that DPI I can't control the movement of the cursor) so went into the mouse settings in control panel and the sensitivity was only at 50% which I swore I turned it up max with my last mouse, cranked it up to 100% then pushed the DPI back down to 4600 and everything felt normal again.
I believe this is a random bug with windows just randomly bugging out?
Cause I've used the Razer naga on an old razer goliathus control mouse pad which is mostly black with some green on it and my laser and optical mouse didn't have an issue with it and I've now had this razer goliathus speed extended edition mouse mat for about a month now which is mostly green with shades of black here and there that and in razer synapse my mouse is specifically calibrated for this mouse pad.
If it was a problem with the mouse mat then there would be a lot of people complaining that these mouse mats are bad but they aren't, specially since this mouse is designed to operate on almost any surface even a towel even my old cmstorm devastator optical mouse could do it.
Aside from that when the issue occurred I noticed my Logitech orion spark G910 keyboard started to act up too all the leds turned off then back on for a brief few seconds however the Logitech gaming software or Razer synapse programs (controls features of Logitech and Razer devices) didn't report any malfunctions or errors, and couldn't be that that software restarted as when Logitech gaming software isn't running the leds default to cyan blue colour rather then the colour I set.
As a technician this entire ordeal is bizarre been around pcs since I was 5 for 21 years and this is the first time I've seen this happen.
I've had dust and hair in the mouse before but they don't act like this and for that to cause the mouse sensitivity settings to reset to default in control panel is unheard of.