No, and not always.
E.g. from my experience, many intelligent and beautiful women prefer the shy type over the boastful sales person becuase it signals you are a thinker and that you take nothing for granted. In that context, is shyness really a disadvantange?
Many employers also think like that.
But can shyness be a sign of a certain degree of imaturity? I think so, more than I subscribe to the idea it's a disorder.
Do you suffer from it and beat yourself up because of your shyness? Then it's a problem, perhaps a small issue with your self-esteem. It can be fixed though. Just like almost anyone can learn math, almost all mental hickups can be fixed, if you have an interest in fixing them.