97 Sierra 2wd Steering Wheel Jumping +or- 10 Degrees

[ollie2009]

I just got a 1997 sierra 1500 SLE 2WD with 118,000KM (74000 miles). The truck is immaculate, and needed nothing for a safety. What I've noticed since getting it though, is that if I am going straight down the highway, and I am applying slight pressure to the left of center (but still travelling straight ahead) the steering wheel will jump about 10 to 15 degrees to the left, therefore steering to the left. The same thing happens to the right, if I am running down the highway with slight pressure to the right. The "Jump" feeling, is like as if I had standard steering and then suddenly had power steering and my hand pressure was not enough to affect standard steering but in powersteering "mode" the wheel moves (jumps) easily. I don't know how else to explain it. I have always done all my own repairs, but my previous truck was an 85 chevy. Any suggestions? I could really use some help here, I'm nervous about my wife driving it.

[gmtech4]

get a steering wheel sensor put in ,at the end of the steering columm