What causes my front end to shake? on 1993 Mitsubishi Mighty Max

When i'm going around 40 mph the front end shakes. When i speed up to around 50 mph it stop.

Asked by for the 1993 Mitsubishi Mighty Max
One of a couple of things. Could be a wheel out of balance or front end alignment problem. Or, you have a failing CV joint which needs replaced. Have tire balance checked first on front tires.