Long before his kook's tour of La Dolce Vita's wilted garden of Hedon earned him the symbolic status of a male MM (a capital distinction previously reserved for Marilyn Monroe), the sweet smell of sexcess had begun to pall on Italy's Marcello Mastroianni. Vita, as the onetime Roman roustabout and Shakespearean player is quick to point out, was his 45th flick in 10 years of self-admitted service as a passive, world-weary seducer. Despite such prima-facie evidence as his finely dissipated good looks and can't-miss bedside manner, Mastroianni firmly insists that this stereotyping is undeserved. He is a stranger to the Via Veneto, Rome's sexual supermarket, has been married for the past 12 of his 36 years and, while making A Very Private Affair with Brigitte Bardot, refused to oblige Rome's wolf-pack press with a public sequel. Intelligent but not intellectual, Mastroianni relies heavily on his directors for characterization -- a shrewd dependence that will soon lead him once again down the primrose path to box-office heaven as star of The Labyrinth, Federico Fellini's extension of La Dolce Vita. But the role that pleases Marcello most is that of a sweaty, mustachioed Sicilian in Pietro Germi's forthcoming brute farce, Divorce, Italian Style. "The public certainly doesn't think of me that way," says celluloid's sated stud, "and that is what makes it interesting."