Michael was reported missing from his home in the North Circular Road area of Belfast.
He was last in contact with his family at around 2 pm on Tuesday, 9 January.
Chief Inspector Stephen Burns said: “It is known that Michael would sometimes frequent the coffee shops in the Boucher Road and Lisburn Road areas of Belfast.
“Have you seen him in and around these areas?
“If so, please contact police on 101, quoting reference number 622 09/01/18.
“Michael is 5’11” tall with dark hair and beard.
“It is believed he is wearing a green puffa jacket, grey jumper and black trousers.”