The talk show, that staple of mid-afternoon and late-night television, is in danger of becoming talked out. Producers from the major shows - Carson, Griffin, Douglas, Snyder - face a common problem: the worsening shortage personages and personalities needed to feed the public's seemingly insatiable appetite for televised chit-chat.

"There just aren't enough good people for this business anymore," observes Tom Snyder show producer Bob Carman. "You hate yourself because you've eaten everyone up so fast. The talk show may not be worn out, but it's sure worn down."

With many familiar celebrity standbys hopelessly over-exposed, new strategies are being put into action. Vince Calandra of the "Mike Douglas Show," for example, is placing ads in the local Philadephia papers to flush out "left-fielders," a polite professional name for such acts as the 26-year-old Philadephia man who imitates the front ends of cars with his face; or the Philly cab driver who makes bird calls through a fountain Pen: or the fellow who plays "The Star Spangled Banner" by making rude noises with the palms of his hands.

And Merv Griffin has now begun re-designing his show around themes - a recent one was Catholic priests who left the church - to help jog his guests into properly scintillating conversations.

Producer Carman recalls with nostalgia his days with Jack Paar in the late '50s, when talk shows were a "new thing" and guests of the highest order - Alexander King. Oscar Levant, Walter Slezak - flocked to the studio.

Today, with the celebrity supply virtually restricted to Hollywood, things are tougher for the talkies. "The '60s were more exciting," Griffin remembers. "There were crises all the time and people were much more flamboyant. I remember the audience used to even scream at us. That was great. Now it's all one by barbeque."

Even some of the familiar pinch hitters, Carman complains, notably Steve Lawrence and Eydie Gorme, now decline many talk-show invitations for fear over-expose will damage their careers. And they might be right - recent studies by Performer Q of Port Washington, N. Y., reveal that constant television appearances can sometimes lower a performer's popularity rating, rather than increase it.

Steve Weisberg can't sing like Steve Lawrence and he doesn't look like Eydie Gorme, but suddenly he's a star.

It began innocently this spring when Weisberg answered an ad in a Philadelphia paper for "novelty acts" placed by Vince Calandra. At this audition Weisberg did his thing - which is to contort his face into the shape of the front ends of cars. Two weeks later he was on national television, bending his nose and mouth into the semblance of classic Edsels, Studebakers and Kaisers.

"The strongest acts we get are the weirdo left-fielders we get through the ads," says Calandra who was once chief talent co-ordinator for Ed Sullivan. "And that Weisberg, he's the most successful of the weirdos."

The appeal of Weisberg's act was such that soon after his Mike Douglas appearance he was booked on the Snyder show, and agents from Hollywood began negotiating a contract on "Laugh-In."

"All I can say is I'm glad my face never matured." Weisberg says with a wry laugh. "I started when I was 3, but people got mad - my mother used to say, "Stop making silly faces." She threatened if I didn't stop my face would freeze - but it hasn't yet."

Weisberg's colleagues on the left-fielder circuit are many - including the unforgettable "Fruitcakes," who on the Douglas show this spring did their three-woman singing act while squishing squashes laid at their feet.

There's also the heart-warming story of Steve Backer, 21, of Glassboro. N. J., who got his stint a couple weeks back by playing the theme to "Rocky" on an imaginary trumpet whiel struting around in boxer-shots and whacking a piece of steak on a string. Becker, a counselor at a local YMCA, now sees his name in lights.

"I'm already a mini-celebrity at home," he says excitedly. "I can really relate to Rocky now. I got my chance I went the distance."

When a talk show runs short of left-fielders, they can turn to Chicago agent Gilbert Miller. His stable includes such acts as the hard-stomping, rope-dancing Argentine Gauchos: Johnny Bomerang, the South Texas coast "beach bum" who throws the Australian boomerang: and the odd fellow who wrestles alligators on talk shows, but has now apparently disappeared into the bayous of Louisiana.

Miller believes novelty acts - he abhors the word weirdo - are going to provide more and more of the talkshow fare as people look for something besides leisure-suited stars and big-breasted starlets. "People are getting boared with celebrities," Miller believes. "You have to have some variety."

Talk shows appeal less even to performers these days - and the problem is over-exposure.

"These people see Elvis, for one, has kept his money high by doing nothing," Carmen explains. "They know their value will go up if they're not seen so often. "That's why these days sometimes you can't get Joe Zilch to appear on the show."

Steve Levitt, who runs Performer Q. a show-business personality popularity rating service used by some talk shows and networks, says some of the most popular celebrities are those who stay away from the shows - people like John Wayne. Robert Redford and Paul Newman. Levitt's findings are based on "consumer panels" of "several hundred families" around the country.

Those who are seen regularly sometimes find the rewards mixed. Before she gained national fame on talk shows in 1975, bosomy Latin starlet Charo was "recognized" by 57 per cent of Levitt's national television sample - and had a "popularity quotient" of 9 per cent. Today, known by 80 per cent, a figure as high as Clint Eastwood's 80 per cent, Charo's popularity is 8 per cent.

"If she was known by 100 per cent of the world, chances are her popularity might go down to 7 or 6 per cent." Levitt says cooly. That paradox makes some performers think twice when invitations to talk shows come in.

Even politicians are shying away, and that trend upsets Phyllis McGrady, the 25-year-old producer of the "Panorama" talk show on WTTG. She is livid over Carter administration officials' reluctance to appear before her cameras. "I stayed here for the Carter administration, but now, well, they're just not coming on the show, the jerks," she says.

White House deputy press secretary Rex Granum explains that the men running the government just don't have the time in the middle of the day to run over to McGrady's Wisconsin Avenue studio. "It's not that there's any reluctance on our part," Granum said. "There is just some difficulty dropping everything in the middle of the afternoon to go on the show."

After 15 years as a talk-show host, Merv Griffin is growing uncomfortable with the old celebrity-oriented talk-show format. Unimpressed by parades of "left-fielders," Griffin since 1972 has been moving towards a new, "magazine" or theme approach to brighten his program.

More recently, Griffin has tried to break the Hollywood mold by filming shows in Las Vegas, Mexico and Israel. Later this year, Griffin plans to move his road show East, shooting for several weeks in New York and at Washington's Ford's Theater.

"We can't be content to sit on our chairs and couches any more," Griffin says.

With his "theme" approach - be it on Washington politics or trans-sexuals - Griffin has hastened the move away from the traditional "one-on-one" talkshow routine. The same approach has been adopted by Phil Donahue," the Chicago-based phenom of the talk shows, whose Readers Digest approach makes up in lively topics what it may lack in big names.

It may be, as Donahue producer Pat McMillan puts it, that the public is no longer interested in merely finding out what stars eat for lunch. The tube, after all, is their medium and the audience, mostly housewives, have a need to see their own personal marriage problems - breast cancer, home economics, marriage crises - discussed on the screen.

McMillan has taken this tack even further than Griffin by having the 200 or so housewives in Donahue's studio audience ask questions of his guests, and, later on, give input about what they would like to see.

"We think the time of the glitter markets is passed," McMillan says. "Our attitude is different - we feel fe have to learn as much from the housewives out there as they can from us. And when you talk every day with 200 of them, boy, you really find out what they want to talk about."