Ready or not, here comes Hitler. Again. The preoccupation of books and movies with Nazi Germany practically constitutes a posthumous Fourth Reich. Two films about the last 10 days of Adolf Hitler have already been made, but that hasn't stopped CBS from rendering a new TV version of "The Bunker," from James P. O'Donnell's best-selling account of Hitler's last 105 days.

The three-hour film, at 8 tonight on Channel 9, may with no hesitancy be called morbid but producer-director George Schaefer has been tediously meticulous in avoiding anything even remotely lurid. There is no "group sex" orgy as in the book, and the suicides of Hitler, Eva Braun, and Herr and Frau Goebbels are kept discreetly off-camera.

Indeed, the whole production is so rigorously somber and austere that it would be very tough going without the fascinating centerpiece of Anthony Hopkins' performance as Der Fuehrer. Hopkins was an unlikely choice, and the part could scarcely be more difficult (perhaps only Jesus is harder to play), but he proves resourceful and magnetic.

Somewhat daringly, the screenplay by John Gay and Hopkins' portrayal give Hitler a dimension beyond horror. He is even seen to be a figure of pathos, quivering and muttering in his underground headquarters, forever being inoculated by doctors, insisting "We shall be victorious" when all evidence is to the contrary, anticipating his death by saying, "One brief moment and I'm free of everything."

No new insights are offered into the pathology of fascism, and the drama could be considered pointless except for the spellbinding way Hopkins interprets Hitler. When enraged, his eyes seem to rattle on their own trajectory, locked into obsessive madness. A few scenes later, waxing avuncular, he reads from a storybook to a group of young children.

It could be argued that to humanize Hitler is to trivialize the horror he masterminded. Along that line, the choice of Susan Blakely to play Eva Braun smacks of box-office vulgarity. But few other concessions to the demands of popular entertainment have been made; the film deserves a certain somber respect, if a begrudging one.

Among the supporting cast of Hitler's ja -men, Richard Jordan's Albert Speer comes out smelling like edelweiss. Author O'Donnell acknowledges the still-living Speer as one of his principal sources for this reconstruction of bunker times. In the opening scene an actor playing O'Donnell says of the drama to follow, "I can't guarantee that what you're about to see is the historical truth," but claims the account will be "as close as we can come." The film never answers the question, "Why should we try coming close, or even plunging back into this period at all?"

Perhaps a moratorium on Hitleriana could be proclaimed, if only for a few months. At the very least, each network could agree to limit itself to no more than six hours of prime-time programming about Nazis each season. That would mean CBS has already reached its quota with "Playing for Time" and "The Bunker." Enough. Otherwise all those comrades who say "Goodbye, My Fuehrer" prior to his suicide might more appropriately have only said "auf Wiedersehen ."