Good sport that she is, the talk show hostess hunkered down on the floor to demonstrate yoga to her television viewers and the zipper on her brand new Gucci pants gave way before millions of startled Americans. And there was the time the irrepressible Cloris Leachman was a guest on the show. She took a seat, gave the hostess a big smile, and inquired: "Tell me, Dinah, how's your sex life? I don't mean just talk show stuff. How is it really?"

Then there was the movie star who said yes, she would come on the show, but only to tell the world of her breakup with the young director who made her a star, and of her determination to go it alone. (Dinah Shore, model of Southern gentility, isn't saying who it [WORD ILLEGIBLE] Cybill Shepherd is

"So we're sitting there, cameras rolling," Shore said in her mellow drawl, "and I said " 'You and so-and-so, I understant that isn't working any more?" She said, 'Oh, no, we're fine, and at breakfast this morning he told me to be sure and give you his love.'

"Well, i was naturally happy for her that they'd patched things up," the ebullient television personality said, "but there went the first 15 minutes of the show"

Those were the bad moments, but they have been few. She's been at this talk show business for eight years now, the last four as the star of the synidcated. 90-minute, five-day-a-week "Dinah!" Before that she was the proprietor of "Dinah's Place," which held down a 30-minute time slow on NBC's daytime schedule for four years. She says she loves it.

Even if she could go back to running a glossy, prime-time variety hour, as she did so successfully in the 1950s, she says she would not.

"This (the talk show) is not as difficult as that. That was seven days a week and the more you rehearsed the better you were. It was absolutely live, and how secure I was when I got into those dance routines was in direct correlation to how much time I spent rehearsing.

"Conversely, in this kind of show, the more spontaneous, the fresher you are, the better the shwo. I think our kind of show has replaced the variety show.The old format was slick, and I don't think that's what people want these days."

Some reference books indicate that Dinah Shore turned 60 last March, although other sources say she is four years younger. Other than to deny, emphatically, that she has turned 60, Shore isn't saying how old she is and would frankly prefer to avoid the subject.

"I'll tell you how old I feel," she offered. "About 37."

Looking at her, even at very close range, one could almost accept that, if you did not know that "da songeoid of da South," as Jimmy Durante called her, has been around since the early 1940s.

She looks terrific: skin tanned to a glowing, honey tone; hair a delicate champagne color; a figure a woman half her age would be pleased to have. Waste no time wondering what Burt Reynolds, ranking Hollywood sex symbol, saw in a woman a generation his senior. When the woman si Dinah Shore, that is apparent.

The much-publicized Dinah & Burt love match ended more than a year ago, and it is another subject Shore is not eager to discuss. She avoids interviews precisely because she does not want to talk about her private life. Obliged to talk to reporters in connection with a switch of channels in New York, she sent out word that she didn't to be asked about Reynolds.

Still, when she was asked why she doesn't want to discuss him, she was surprisingly forthcoming. "There isn't anything to say," she said. "Those things, they're wonderful when they are there. It was great while it lasted, and it still is wonderful, in its way. But when it starts to change, it's better for both of you to recognize it. It's difficult to explain to people. We see each other occasionally. We were very close, and we're not."

Her voice took on a certain nervousness that suggested that that particular subject was not only awkward but painful; it belies the stories that termed their romance a press agent's concoction or merely a superficial matter of convenience.

Burt Reynolds is not likely to be a guest on "Dinah!" anytime soon. "That would be uncomfortable." Shore said, "and, well, dumb." But George Montgomery, who was a Burt Reynolds figure to an earlier generaton of moviegoers and to whom Shore was married for 18 years, was a recent guest on the show.

"I wanted him on for a long time," Shore said, "but I was afraid of it, because I didn't want to exploit our past or our children. But he has become such a talented sculptor that I just thought he should have a chance to show his work.

"We're good friends. We're not sickening about it, but we're good friends. He likes me, and I like him, and we did raise two children together. Still, we were both nervous wrecks. He wouldn't let up on me. Just kept ribbing me, and I kept ribbing him.

"He said: "Why are you asking me all these questions? You know all the answers, and everyone here knows you do.' And then he pointed to his sculptures and said. 'See, this is what I was doing when you thought I was out doing something else.' I said, 'That isn't all you were doing.'"

"But," she said with laughter, "it was a lovely show. Very sweet, and I do hope they play that one again."