What is the Meaning of the Expression
CATCH ONESELF DOING SOMETHING?

Definition:

to suddenly see, or understand, that you are doing something

Examples:

1. The other day I caught myself thinking about my grandmother. She has been gone for years, and I still miss her.

2. Sometimes I catch myself doing something my mother used to do when I was a child, and I think, “I am becoming my mom!”

 

Note:   Replace oneself with the reflexive pronoun that fits the meaning.