Acting should feel like an out of body experience. Very surreal and almost all based on instincts. This is what separates great actors from mediocre. The ability to let go and fully engulf in the character is key.
When an actor receives their lines they read through without acting. Then memorizing . THEN APPLY ACTING.
When acting a scene with another actor or actors is when the full experience takes place. The feeling can be so intense actors find it difficult to break from character. Some actors like staying in character throughout the filming process. Other can switch on and off as needed.