I found this summary on MakeItUltra. He concludes by make it clear that this summary is not a diagnoses or meant to help one self-diagnose a personality disorder.  Here’s a short quote:

“A covert narcissist is a narcissist who suffers from low self-esteem. He or she is seeking the same glory and power as the classic narcissist, but does not possess the same outwardly bravado. They have all the attributes of an overt narcissist but hide behind many masks. In my clinical experience, those who permit a covert narcissist into their lives later spend years unraveling the chaos that has been spun around them.”

How to Spot the Shy Narcissist