intermittent steering noise (1987 260E)
 

I have been having intermittent steering noise. and its kinda hard to reproduce. Occurs after driving for a few minutes. Say I drive a bit, then make a steering turn with the wheel I can hear a low sounding noise like rubber rubbing. Then it would go away when I try to continue wiggle the wheel. Drive a bit more come to a stop light and wiggle the wheel and can hear the noise again, the wiggling motion will clear the noise in that it will now disappears. I must then drive a bit more to reproduce the noise. In order words, the wiggling motion appears to have shake out the noise.
Is this a bad steering rack? Or bushings? stumped!! TIA