Only doubt can build confidence.
If you believe that confidence is a random state of mind and that you think you are a confident person, I'll say you're superstitious.
Confidence, for aspies have to be built from the ground up. The only way to achieve this it to use doubt: whenever you realize something is strange, illogical, odd, interesting, take a second to ask questions and find the good one why it is happening. If you can, make an hypothesis. It is very important to use a significant piece of reality, because it makes your doubts focused and set in a context that may contains answers, don't doubt out of the blue, it's irrelevant and counter productive. And don't worry because the world has not changed while you were thinking.
The more you will practice the more connections between the hypothesis you will make, the more able you will be able to make probability bets, the more comfortable with surprise and mistakes you will be. The more open you will be to change. It will go faster and faster, the system will keep itself healthy and sound and self confidence will emerge from that.
I'm the most doubtful and confident man of the planet earth.