Shaking

How do I explain my shaking arm? My left shoulder is ‘freezing’ not frozen. But I have muscle wasting. Because of this I don’t have the strength and power in my shoulder and arm that I had. I try and hold my left hand still when I am holding the phone and drawing, or holding my tablet or even while drawing on the computer. My hand and arm shakes and I can’t draw a straight line! See attempts above. I am doing the exercises but I’m worried it won’t improve. Does anyone else have this problem?