Here's why:
* "Going" is the present participle of the verb "to go," but in this sentence, it acts as an adjective modifying the pronoun "I."
* "Going" tells us what the speaker is doing (in motion), which functions as an adverbial element.
So, the sentence can be rewritten as: "I am going (in a state of movement)."
Let me know if you'd like to explore other parts of speech!