This is the 3604th most frequent Spanish word.
m
In Spanish, "m" is the 13th letter of the alphabet.
In this sentence, 'me' is a pronoun used to indicate the self, equivalent to 'myself' or 'me' in English.
Me llamo María.
My name is María.
Here, 'en' describes location and 'mientras' indicates time, unrelated to 'm'. 'Me estuve' isn't used here specifically.'
Estuve en casa mientras llovía.
I was at home while it was raining.
In this sentence, 'me' is a reflexive pronoun indicating that the subject is performing the action on themselves.