Originally Posted by Tackleberry1
Could be a great many things. Short of a nuerogical exam, I'd suggest a "weak side" stance.
Take a 1/2 step forward with your off side foot. This will turn your weak shoulder toward the target.
As you present your pistol to the target you'll be pressing your strong side bicept into your strong side pectoral muscle. Now raise your arm up above your peck and drop your arm back to perpendicular. This will rest your bicept on your peck and increase the reach of your weak hand allowing it to put strong steady back pressure on your firing hand.
Doing it right should take the shake away and allow you to shoot more accurately.
You know I use a very similar stance when I'm not feeling 100% I have back issues and stability is not always as easy as it should be. So if I see myself being a little unsteady I'll adjust and it does wonders for my shooting.
To the OP it might be nerves though. You say you are not pistol shooting as often being a long gun shooter. It might be apprehension sneaking in and causing a reaction. It might be worth getting checked out just to know though.
You said you where going to try shooting alone. That might take some pressure off you that you might not even be aware of. So that is a good idea. The stance Tack talked about is a little funky when you first try it but I've found it to get very natural really quick.