My ABS would turn on periodically for a couple of months before it started coming on every time I start moving, like it does now. It would usually come on when the right front wheel hit a bump in the road; even small seams and highway transitions could do it. It turns out that the right front wheel speed sensor's wire had torn out of it's 90° angle boot. I haven't investigated further into the repair process because I work in a black hole that sucks up all of my time... this is my third 14-hour day in a row, one more tomorrow.
In the beginning, the light would turn back off if the wire made another connection to the sensor.
Good night to all of my fellow ABS-less drivers.