Grip pressure - not mechanical flaws - is the biggest factor when you're nervous. You unconsciously grip it tighter, which keeps you from making a smooth swing with a natural release. Keep your grip pressure light, and you'll be surprised how much your mechanics stabilize.
When I'm swinging the club at my best, it's because I'm not thinking about mechanics at all. I feel like my body is loose. My arms are soft in front of me when I'm setting up, and my chest and shoulders feel as if they can move and turn easily.