At age 28, Evonne Goolagong Cawley is happily married, mother of a daughter who is going on 3 but looks much older, and the fourth-best woman tennis player in the world.

Most of her colleagues seem to think she is about ready to put aside her rackets and devote herself full time to family life, but Goolagong -- an enchantress in sneakers who always was full of little surprises -- seems to have other ideas.

Why should she retire to her 70-acre estate on Hilton Head Island, S.C., she wonders, until daughter Kelly is ready to go to school? That will be another two years. Practically a tennis lifetime.

After two seasons of recurring injury and illness that interrupted her tennis just when it seemed to be soaring toward a high level of consistency, the lithe Australian is fit again, and apparently eager to challenge Martina Navratilova, Chris Evert Lloyd and Tracy Austin for supremacy in the game she plays with such incomparable grace.

Goolagong is starting 1980 trim, sleek and fast. She is playing well, as she demonstrated yesterday in the opening match of the $250,000 Colgate Series Championship at Capital Centre.

Though she had played only one match since October -- the first round of a November tournament in Melbourne before defaulting with flu that forced her to withdraw from two additional tournaments -- she breezed past distracted and erring Regina Marsikova, 6-1, 6-1, in less than an hour.

It was a heartening performance for her many fans, because a year ago Goolagong was unable to run. That was a bit like a bird unable to fly.

Running is what Goolagong had always done best. She was so swift, so balletic, so light of foot that her feet hardly seemed to touch the ground. She was the most ethereal of tennis players. A sprite. A zephyr.

For her not to be able to run seemed unreal. But for almost nine months, she could not. A foot injury nearly ended her career.

"I saw a specialist in New York (Dr. John Marshall, a noted orthopedic surgeon who has treated many tennis players) and he gave me a lot of stretching and conditioning exercises to do.

"But I really didn't think it would ever get better. I was getting quite despondent about it last winter because the exercises were boring, and I was getting very tired of riding a stationary bicycle and not being able to play. Actually, I didn't think I'd ever play again, it carried on for so long. I was getting that discouraged.

"But then one day out of the blue it just cleared up. Dr. Marshall had told me it would do that: 'One day you'll wake up, and suddenly you won't feel anything.' The next thing I knew, I was jumping up for smashes. I couldn't stop running then. . . ."

That is the way the public remembered Goolagong as the honey-skinned, one-eighth aboriginal girl who could never stop running or smiling as she played shots that made the heart skip a beat.

She played that way in winning two tournaments before Wimbledon, and up to the semifinals there, where she came up disappointingly flat against Evert Lloyd. Her old rival beat her again in the quarterfinals of the U.S. Open.

But last fall, Goolagong seemed herself again as she swooped through the field to win the U.S. Indoors at Minneapolis (beating Renee Richards, Betty Stove, Virginia Wade, Tracy Austin and Dianne Fromholtz) and a tournament at Tampa (beating Wendy Turnbull, Austin, and Wade in the last three rounds). In all, she was 54-9 in singles and won $187,407 in prize money in 15 tournaments before the flu prematurely ended her season.

Now she is back. But her chief rivals, though they respect her immensely, seem to doubt that she will be a factor in 1980.

And what about Goolagong herself? Does she feel motivated?

"I do. I think when I first got married to Roger (in June 1975) is when I started to produce by best tennis. I think '76 was actually my best year, when I played my most consistent tennis. Now that I have a family I feel a lot more secure in myself, and I feel a lot more professional about tennis than I did before.I feel I can go ahead and try harder and do my best.

"I feel better with a base and some roots, more confident in myself . . . It's just unfortunate that I've had to sort of stop and start all the time (because of injuries). That hasn't helped me. I think some people were sort of thinking that my marriage and family are maybe the cause of a bit of slump, but it's just that I've been stopping and starting so much. oI think my marriage and family have helped me.

"I haven't really set an exact date when I'm going to suddenly start fading away in tournaments," she continued, giggling. "I know that once Kelly goes to school, I'll stop. But at the same time, I enjoy tennis very much, and we haven't planned an exact date when I'm going to have more children. At the moment I'm very keen on playing. I'm sort of all fired up. I just hope I don't have to stop again for awhile."

"If she wants to stop and have another baby, fine. It's totally up to her.

But I think right now she's keen to keep playing," said husband Roger Cawley, a British metal broker who now handles his wife's business affairs.

"I never quite know how she feels about it. I thought she'd pack it in after her injury. I was surprised that she wanted to come back. I think if it hadn't come around when it did, if she was still struggling along, she would have quit. But she's running well now." w