No, Elon Musk's initials are not ERM.
His full legal name is Elon Reeve Musk, so the standard initials (first name + middle name + last name) would be E. R. M. or simply ERM.
People sometimes write it as ERM (especially in contexts like email addresses or quick references), and there was even a reported government email for his DOGE role using something like erm71@... — but it's definitely not "erm" as a standalone set of initials in the way you might be asking (like if it were just two letters or something else).
So close, but yes — Elon Reeve Musk → ERM. 😄