From Longman Dictionary of Contemporary Englishsettle back phrasal verbto lean back in a bed or chair, and relax and enjoy yourself Vera settled back to enjoy the film. → settle→ See Verb table
Examples from the Corpus
settle back• As she settled back down it continued to cook and burst into flames.• She settled back in the seat.• Afterward, though, many activists settled back into a celebratory kind of daze.• She would settle back into her safe routine and forget this time.• That done he settled back, letting the young Prince speak.• Müller made soothing noises while Eloise moved seats to comfort her and then he settled back to plan what he must do. 