MBTI-wise, extroverted and introverted are not 'shy' and 'outgoing.' Introvert and extrovert refer to habits of perception. Are you primarily internalizing your dominant cognitive processes or are you externalizing them? These primary attitudes are the result of complicated subconscious processes, so flipping your type from 'extrovert' to 'introvert' or vice versa would require a re-ordering of all your functions that would require either an extreme trigger of some kind--- physical or psychological trauma or some heavy duty drug use. Basically, something that would require you to re-wire the way you think from the bottom (subconscious) up (conscious). And that rarely happens.
However, if you mean extroverted and introverted in terms of social attitudes, those flip-flop all the time.
You can change your attitudes (the way you approach life and what you pay attention to) very easily but your personality (the way you process your thoughts and feelings, your subconscious needs, beliefs motivations, the psychological strengths and weaknesses you've cultivated over a significant time) mostly sticks with you for life fully intact after a certain age. Nobody agrees on what age it is exactly, but 18-25 is the typically cited window.
I am aware that we are discussing typology, who is based on the conscius and unconscious, and on the introverted and extroverted functions..
Hovewer, the thing with the unconscious is a concept which has no scientific validation whatsoever.
It is invented by psychologists. Some would argue that there are some strong psychologicl arguments for the existence of the unconscious mind. Bu then there are also some pretty strong arguments that the unconscious mind is a inexistent thing.
I take the second stance. I don't think there is such a thing as the unconscious.
And it would also be that I, as a religious person, and many other religious psychologists, see this very importantly tied to morality and ethics. Secular psychologists exclude the moral factor in a objective sense, making it as a sort of subjective psychological approach. Thus, if morality plays a very important part in shaping the psyche of a person, most of the psychological theories are fundamentaly flawed.
What you described here is the inferior function at work. A lot of T types, especially the types with Ti or Te as a dominant function, have Fe or Fi as their inferior and thus, the phenomenon that you describe is not odd at all. The journey of the personality type is finding a way to balance the conscious and subconscious pulls of your dominant-function pair. For ESTJ, that's Te-Fi. They act out their subconscious need for moral rigor and order informed by their Fi via their dominant extroverted T that is, of course, is often expressed as harder than the typical dominant F function.
I didn't said this phenomenon, which is that the logical types are often more responsable and mature in their ethical behaviour, is something odd.
It can appear paradoxical because Feeling types tend to come of as more caring, understanding, ethical.
While logical types can appear as cold, whithout understanding, and to some people even unethical.
For example, INTJs are described many times as having "death stares", or having traits associated with sociopathy, or being overly cold and unemotional. Which is completly not true. Is that kind of silly thinking that give raise to untruthful stereotypes.
Now let's take for example Hitler. He was a INFJ. I know there are so many saying that he actualy was a ENFJ, or a ENTJ, but I don't think its true. People have described him as being "compassionate", "gentle", "kind", "understanding", "like a father" having a "warmth" and all these good attributes. And there was standing one of the greatest dictators of all times...
The issue is this: feelings /=/ ethics.
But feelings = empathy.
But then empathy /=/ ethics.
So a moral/ethical person can be either logical, either intuitive, either sensor, or a feeling type of person.
That's why I think paradoxical, ESTJs are one of the most responsable types, if not the most responsable, yet they are primarely a logical type.