[1.16.5] player.setMotion() is not smooth enough

What Im trying to do is to implement a "dash" mechanic on a Shift button.
 

@SubscribeEvent
    public static void onEvent(InputEvent.KeyInputEvent event){
        KeyBinding runBinding = Minecraft.getInstance().gameSettings.keyBindSprint;
        int key = event.getKey();
        int runKey = runBinding.getKey().getKeyCode();
        ClientPlayerEntity player = Minecraft.getInstance().player;
        if (key == runKey){
            //some checks, and then:
            float yaw = player.rotationYaw;
            float x = -MathHelper.sin(yaw * 0.017453292F);
            float z = MathHelper.cos(yaw * 0.017453292F);
            double groundMotion = 5, airMotion = 2;
            if (player.isOnGround())
                player.setMotion(new Vector3d(x * groundMotion, 0, z * groundMotion));
            else
                player.setMotion(new Vector3d(x * airMotion, 0, z * airMotion));
        }
    }

And this code works. The problem is, it causes a lot of lag when the setMotion() is called - my fps drops from 60 to 50-40 and the dash movement looks discrete. I wonder why is it so and how it can be improved...