What is a "WAG"?I'm going to offer a WAG here, and propose that the problem is caused by a faulty electrical connection to one or more of the sensors (but possibly only one would need to be faulty). Your description of how the problem manifests is what makes me think this. If a connection is faulty, when it is cold it will not conduct current properly and will send a faulty signal to the EPS control unit. Virtually ALL of these systems use voltage values to interpret as things to react to, and, to correct. As the car is driven, things warm up, and possibly there is maybe a tiny bit of movement in a faulty connection that improves conductivity, restoring the sensor voltage value(s) to "normal".
Now, I have NO knowledge of this particular system, but I'd carefully examine ALL connections to the steering sensors. Possibly, just unplugging them and replugging them in would be all that is needed. Additionally, is there some kind of grounding wire that may have a faulty connection to the car's frame?
I doubt a sensor would self-correct if it was faulty.
This all sounds to me much like the way faulty O2 and transmission sensor values behave when there is a poor circuit connection.