It’d help if you included a screen shot of the events that move the object to see exactly what you are doing, but I’ll go on the assumption you are adding an (non-physics) instant force.
When you apply an instant force, it sends the object in the direction of the force for a frame. There will be a point in time when the object is almost at the target, but not quite. Adding the instant force pushes it past and beyond the target
The next frame, a force is again applied, but this time back towards the target (so in the opposite direction to what it was before). Because the final spot of the object will never be exactly on the target (your object’s position will have a large decimal tail), this back and forth, or oscillation, occurs repeatedly, giving it the shaking effect.