Good advice from Neil. Normally you want a still head but every so often it helps to move it slightly to get a better view of the shot, and see if you're lined up correctly to drill it in. [Cue perfect aim plug]. Once you settle down you can go back to keeping a still head.
If anything feels wrong at all, or slightly uncomfortable, shuffle your feet. You don't even need to move them really, just lift 'em and replant them until you're sure you're 100% comfortable and lined up in the direction you want. You may not feel like you changed anything but it can help.
Lastly, before a game, ask your opponent if they mind waiting a sec and drill in a few real fast. Set up some sort of ugly cuts and drive them in with 0 thought and just 1 practice stroke. Make a few to get your confidence back.