I think it's a sensor problem, I have and always have had this problem on my car, I think what is happening is one of the sensors is giving a duff input and it thinks the wheels are locking, remove and clean all four wheel sensors (It should be done anyway every so often so as to prevent problems.) This is what I have done but my front offside sensor is stuck and I think this may be the one causing a problem.

Also dirt in the teeth of the ring wheel should be removed.

Also a discrepancy between the front and rear wheel speed can cause problems.

Martin