An intensive pronoun is a pronoun used to add emphasis to a statement; for example,
Intensive pronouns look exactly like reflexive pronouns but intensive pronouns do not have a noun function. For example, compare:
The first is intensive. The second is reflexive since it is the object of “nominated”. If you can assign one of the noun functions to it, then it is reflexive, not intensive.
When the pronoun αυτος is in the nominative case and agrees with the noun, then it is an intensive pronoun; see BBG 12.9 or here.