Who I am?
As I said before, Who I am is usually a part of a sentence or indirect question. We change the order of the subject and the verb when we use indirect questions.
Direct question: Who am I?
Indirect question: Do you know who I am?
In this second question, the meaning is different from the first question. In the first question, you are questioning your existence. The second question means that the speaker believes he/she is a person of importance and is surprised that the other person is not aware of this.
More Examples:
I don’t know who I am.
Can you tell me who I am?
Introducing yourself
If you are introducing yourself in a presentation it is better to use “Who I am”, Then you can explain the person you are and it sounds more confident than “Who am I?”.