Before, it was believed that shyness was caused by the type of environment that a child was exposed to. Today though, scientists have found that a child's basic temperament is inborn. In other words, some children are born to be outgoing and assertive, while others come into the world shy and reserved.
Your child is probably one of the latter type of children – he or she is naturally bashful, and will take time before trying out anything new.
There is a difference between shyness and separation anxiety though. If your toddler suddenly becomes more wary of strangers, and really doesn't like the idea of letting you out of their sight, then it is separation anxiety. Most children go through this phase between the ages of 7 and 18 months, some of them continuing this way until they are about three.