car travel all over the roadf

On normal road condition car travel find next when car come onto snow cover or mix condition wet snow ,part clear and part snow cover the car steering or wheel drive wants to travel in zing sag or back and forth dir creation . You have to fight with the steering to keep the car going straight. With the 4wd drive switch on or off does change the problem still there. esp switch on or off the same . this car under winter condition is not safe to drive we have winter tire on,