Rep. Joseph L. Fisher, casting aside his normally reserved, scholarly manner, spoke heatedly about some most exasperating moments in his campaign to retain his congressional seat in Northern Virginia's 10th District.

"He's making a big thing out of free congressional parking at National Airport - and I have no occasion to use it," said Fisher, the Democratic incumbent who is running for his third term.

The "he" is Fisher's Republican challenger, Frank R. Wolf, who has forced the congressman to discuss airport parking and what Fisher says are other nonissues" such as whether Fisher writes and signs his own letters to constituents. (He doesn't.)

"It's ridiculous. It's stupid." said Fisher, a former economist and professor. "I don't think you can make a campaign out of this.

Fisher, 64, is trying to get the 39-year-old Wolf to talk about specific campaign concerns and programs, but so far, he says, he has had to waste his time "coping with Wolf's yipping and yapping at my heels."

Wolf, an Arlington attorney, and is making a good showing in his race against Fisher and hopes to recapture the congressional seat that conservative Joel T. Broyhill lost to Fisher in a stunning upset in 1974.

"But Fisher, long active in Northern Virginia planning and government and the chairman of the Arlington County Board during his 10-year service on it, is widely seen as the front-runner.

A popular and respected congressman with a reputation for outstanding service to constituents, Fisher has builit up considerable legislative clout as a member of both the powerful House Ways and Means Committee and the Budget Committee. He also serves on a special Ad Hoc Committee on Energy.

"He's one of the half dozen best people on the Ways and Means Committee, and he has worked effectively for better and fairer distribution of taxes and to plug tax loopholes," according to Bill Pietz, staff attorney for the Washington-based Public Citizen Tax Reform Research Group.

Fisher will "analyze each issue more carefully than most and not shoot from the hip like most of the others," said Pietz. The congressman's background in economics usually means "that when he comes to a decision, he takes some others with him because they know he votes his conscience."

Michael Barnes, the Democrat who is challenging incumbent Republican Rep. Newton Steers in Montgomery County, has called Fisher a "gutsy" lawmaker whom he would most like to emulate if elected.

That characterization stems from Fisher's support for President Carter's recently enacated civil service reforms and his consistent backing of energy conservation programs, neither of which is a favorite subject with many of his constituents.

Fisher said he knew his support for civil service reforms would be unpopular, "but I voted the way I felt. There's much more fear of this than will turn out to be justified." As for his energy stance, Fisher said he is "willing to dish out the unpleasant medicine to get on with conservation."

So it particularly bothers him, Fisher said, "when my opponent doesn't spend too much time addressing the issues in a constructive way."

Aware that Wolf is making much of Fisher's liberal voting record in Congress, Fisher said he sees himself as "pursuing a moderately conservative fiscal policy" aimed at cutting inflation.

"But I try to disregard these labels and talk about where I stand, how I've voted and what I plan to do," said Fisher. Voters "will find I'm fairly pragmatic," he said.

"Born in Pawtucket, R.I., Fisher graduated from Bowdoin College. He holds a master's degree in education from George Washington University and a doctorate in economics from Harvard University.

Once president of Resources for the Future, Inc., a private foundation for research and education on natural resources and conservation issues, Fisher was an economist for the State Department and executive officer and senior economist for the Council of Economic Advisers before getting involved in Arlington County government.

Now in the thick of writing tax reform and energy conservation legislation, Fisher said he is seen as "a tough cookie" by some of the Republican organizations and special interest groups who have contributed heavily to Wolf's campaign.

"These groups like Texaco (whose public action committee gave Wolf $500) and so could care less about Wolf, but they want me off my committees," said Fisher.

Fisher has restricted the amount of money he will accept from individuals and firms - below what federal regulations permit - in an effort to avoid being accused of being influenced by what he calls "these outside pressure groups." As a result, he said, he won't be able to buy television time for campaign ads as Wolf has done.

Wolf has said Fisher solicited contributions from some of the same groups that contributed to him and has charged that Fisher has not been reluctant to accept donations from labor organizations.

Assessing his accomplishments in Congress, Fisher points to his work on a law overhauling the 1790-passed diplomatic immunity statute that had previously prevented U.S. citizens, some from his district, from collecting automobile accident damages from diplomats and their staffs. Fisher also said he helped pass a tax reduction bill this last session of Congress and has done "a lot of meat and potatoes stuff" at the local level to bring services and federal funds to his district.

"I try to represent my constituents in a good old-fashioned way, and I also try to do my work and be effective on the national level," said Fisher.

That effectiveness would be drastically affected, Fisher has argued, if he crusaded to ban free congressional parking at National Airport. "I couldn't imagine anything that would make me more unpopular with my colleagues."

Fisher said it "would be all right by me" to observe a Wolf-suggested limitation of 12 years in office, "but there's no way you can elevate this into a major campaign issue. I think he'd better worry about getting elected once."

So while Wolf keeps giving what Fisher calls "his stock political speech," Fisher said he will continue to issue "careful statements" on the issues of inflation, tax reform and energy conservation.

"I just can't give a quick, flip answer to their questions," said Fisher. "If the answers were simple, we'd have the problems figured out by now."