Your teeth cannot straighten on their own, not without braces. Are you asking that if you get braces, your teeth will be less likely to migrate after they are removed? Some people's teeth move after braces, others do not. Mine have only moved a little and don't seem to be moving more, so I never bothered wearing my retainer.
Your teeth position may have more to do with your parents nutrition prior to your birth than yours as a child.
You are also often given a retainer to wear overnight at least a couple times a week, but they never tell you what to do when you need a new set (mine are pretty gross after 9 years).