Is yours a reflexive pronoun

No, the Word 'yours' is a possessive pronoun, a Word that takes the place of a noun that belongs to someone or something.

The corresponding, second person, reflexive pronoun is yourself.

A reflexive pronoun 'reflects' back to its antecedent.

Examples:

That copy of the memo is yours. (possessive pronoun, takes the place of the noun 'copy' belonging to the person spoken to)

You should fix yourself some lunch. (reflexive pronoun, reflects back to the pronoun 'you', the person spoken to)