It could be a yaw rate sensor problem. Back when I worked at Lexus we had a campain to replace those little (but very expensive) sensors. If they weren't calibrated properly, the car would do as you described. I would bring it to the dealer. This doesn't sound like anything you could fix at home. I think you can disable the system by disconnecting a wheel speed sensor to shut it down, but don't quote me on that (no liability here!). This will undoubtedly set codes for traction control.
