Mood Swings and behavioural issues.

Hello Doctor I am seeking guidance regarding my 70-year-old father, a retired government servant, who has shown noticeable changes in his behaviour since his retirement. He often seems disinterested in family conversations, preferring to look at his mobile instead. He rarely follows any suggestions from family members but tends to listen and act on advice from outsiders, even strangers. Additionally, he frequently seeks reasons to leave the house and spends considerable time outside. At family dinners in restaurants , he finishes his meal quickly and engages more with the hotel staff than with us. Despite a stress-free life and a supportive family, we are unsure about the cause of these behavioural changes and would appreciate any insights or recommendations. Thank in advance you for your help.