Lindsay Wagner still doesn't know how it happened. One minute she was driving her sports car on Coldwater Canyon, the next she had crashed into a tree, the car de­molished.

Within those seconds a multimillion-dollar television se­ries and her own acting career hung in the balance. A month later, she has returned to The Bionic Woman, her wounds healed, the series and her career intact.

It was the kind of happening that television networks and production companies dread. The Bionic Woman, an offshoot of The Six Million Dollar Man, had its premiere on ABC on January 14 and proved an instant success. Only four days later, the star of the series had her accident.

"It was the most absurd experience of my life," said the actress. "There's no way I can explain it. I hadn't been drinking. I had just gotten up on a Sunday, so I was com­pletely rested. The sun was shining and I was only going 30 miles per hour.

CAR WAS TOTALLED

"What happened? Did I look away at the wrong moment? Was something wrong with the car? It was so ruined that there is no way of checking, the insurance company told me."

Miss Wagner, 26, was in the midst of filming the fourth episode of The Bionic Woman. She and boyfriend Michael Brandon had gone out to buy some groceries. They were returning when the accident happened. Her first reaction: she couldn't breathe.

"I had the wind knocked out of me, and it had never happened to me before," she recalled. "I thought perhaps my ribs had punctured my lungs. It seemed so weird; I couldn't believe it was happening to me.

"Fortunately I had the presence of mind to say to myself, 'I can't breathe. What'll I do? Try the breathing exercises I learned in yoga.' I started taking short breaths, and it worked.

"I looked at myself in the side-view mirror. Oh, God, I had three lips. I didn't want to look that way. I looked over to Michael. He was unconscious, with his head cut open. I didn't want to look that way, either. So I went back to gazing up at the tree."

With the luck akin to that of the Bionic Woman, the first person to arrive at the scene was a former ambu­lance attendant who administered first aid. The second was a surgeon who lived nearby; he checked for internal injuries.

"We were lucky in all respects," the actress said. "My car is a '68, and the seat springs have never been re­placed. Michael and I were so close to the ground that we weren't thrown out of the car. We didn't wear seat belts, either."

Her head was split open but the skull wasn't fractured. Despite the lip gash, she lost no teeth. Actor Brandon's temple injury was more serious. It required bone and plas­tic surgery.

SLIGHT SCAR AS EVIDENCE

Filming at Universal Studios was suspended for two weeks, then Miss Wagner returned to finish episode four. After another four days off, the regular schedule resumed. Fortunately, two weeks of Winter Olympics preemptions an ABC gave the series more time to catch up.

Miss Wagner displays only a slight scar as evidence of the accident. Despite remaining aches and bruises, she is back at full speed in a role that ranks with Angie Dickin­son's Police Woman as the most strenuous for a female TV star.

Lindsay Wagner was enjoying a promising career in movies, especially with her role in "The Paper Chase," then elected to undertake an exhausting series. Why?

"Aside from the money, which is very good, I thought it would be good for me at this stage in my career. The con­tract guarantees me a movie a year, so I won't lose my hold on features. Meanwhile, I'm getting a great deal of exposure and I'm able to display my versatility. Unlike Steve Austin of The Six Million Dollar Man, the Bionic Woman doesn't work strictly for the government, so she can do a lot more things."

BOB THOMAS, Associated Press