go into (one's) act
To start acting as one usually does. A: "Your mom is always such a great hostess." B: "Honestly, she was stressed all day, but as soon as the guests started arriving, she went right into her act." I know you're really a softie, so don't go into your act—you don't have to pretend to be a tough guy around me.
go into one's act
Fig. to begin to behave in a way typical to oneself. The curtain opened and Steve went into his act.