Almost since the day he arrived in the international tennis scene five years ago as a 15-year-old prodigy, Bjorn Borg has been described in a manner befitting a young Swede with a pulse rate of 35: stolid, unflappable, imperturbable, unemotional icy.

Then suddenly while winning the U.S. Indoor Championship at Memphis the week before last he merited new and decidely uncharacteristic adjective: surly, temperamental, impetuous, tetchy.

Hence, an intriguing question as the Wimbledon champion makes his Washington debut in the $100.000 Volvo Classic, which starts in earnest Monday at George Washington University Smith Center after some celebrity preliminaries today.

Will local fans see the Dr. Jekyll Borg - calm, expressinoless, content to let his topspin strokes speak for him - or the Mr. Hyde of Memphis, who might have been the recipient of a snarl transpiant from Ilie Nastase?

Though unlikely, the latter is possible especially since Borg could be irritable from acute jet lag. He will be arriving here, probably Tuesday from a Grand Prix tournament in South Africa, and is scheduled to open againt Californian Hank Pfister on Wednesday.

Borg is the No. 1 seed in the 32-man Volvo tournament, also a Grand Prix event, but several factors suggest that he should not be a heavy favorite.

The flight from Johannesburg is exhausting for mind and body. The difference in playing conditions, especially altitude (Johannesburg is 7,000 feet above sea level), poses a tricky adjustment.And in Borg's half of the draw are such potentially troublesome "spoilers" as Americans Bob Lutz (seeded No. 6), Cliff Richey (No. 7) Jeff Borowiak and Tom Gorman, plus 1976 Australian Open champ Mark Edmondson.

Some smart money will be the No. 2, 3 and 4 seeds, Raul Rimarez, Brian Gottfried and Roscoe Tanner, Rimarez took a vacation at home in Mexico last week, while Gottfried and Tanner have been representing the U.S. against Australia in the World Cup at Hartford this weekend.

Ramirez 23, the defending Grand Prix champion, begins his quest for the $20,000 first prize against Haroon Rahim.

Gottfried, 25, winner of two recent Grand Prix events and runner-up to Borg at Memphis, has a tough first-round opponent in Australian Davis Cupper Ross Case. Tanner, 25, the AUstralian Open winner, opens against 31-year-old lefthander Tomaz Koch.

And what about Borg's new reputation? Its the erstwhile "Teen Angel" getting cranky now that he's a hoary 20?

"I spent some time with him last weekend and he was a bit touchy, on court and off. Not like himself at all," said Peter Curtis, the amiable former British Davis Cupper who ran the tournament in Memphis, the hometwon he adopted after a brief fling as a promoter/entrepreneur in Washington.

Borg demanded the removal of an official who called a second-serve footfault against him in a match against Borowiak, a second-round pairing likely to be repeated here. Borg threatened to walk off, a gesture as out of character for him as putting catsup on pickled herring.

The next evening he reacted sourly to a public address announcer who named among Borg's defeated opponents the official he had humiliated, and nearly blew his match against John Lloyd.

He was down 0-l, 0-1 when his coach, Swedish Davis Cup captain Lennart Bergelin, scolded him and informed him that the announcer - who, according to Curtis, "has made several earlier blunders" - had been fired.

Later Borg snapped that he was going to withdraw from Johannesburg, but several anguished calls from the tournament director there dissuaded him.

"I think his anusual behavier was the result of his not having played much tournament tennis recently, had having a lawsuit hanging over him," ventured Curtis. "He was really nervous worried that he was going to lose early on."

World Championship Tennis (WTC) last month filed a $5.7-million suit against Borg his agent a Colgate-Palmolive, sponsors of the Grand Prix. It charges that Borg renewed on a commitment to play the WCT tournament series this year to compete in the Granf Prix series instead.

While most of the pros begin play Monday there are four "celebrity" matches scheduled today at Smith Center, starting at 2 p.m. followed by the final qualifying match at 5 p.m.

The celebrity field includes Withelm Watch meister. Swedish ambassador to the U.S. who promisses to be stolid and not ask forany linesmen to be replaced.