Might not be at all but do you drink any caffeinated drinks within a few hours of decorating?
Coffee, tea, pop?
I was getting really frustrated with my shaky hands then someone who did murals on wall was talking at a party I was at and she mentioned how the murals could take 2-3 days for her and the worst part was she couldn't have coffee to keep her energy up because her hands would shake.
So I stopped drinking coffee on days I was decorating ....no shakes.
I know this might not be the issue but thought I would share my shaky hands fix