Just as President Reagan and Congress are starting to breathe more easily over economic recovery, some of the most sensitive political antennae on Capitol Hill are picking up new distress signals from voters.

These signals range from mounting concern about foreign policy, especially possible military intervention in Central America, to new fears that rising interest rates may jeopardize economic recovery.

A widening concern over foreign policy, including arms control, military aid to El Salvador and covert assistance to Nicaraguan rebels, emerged in telephone interviews with a dozen House freshmen as they returned to Washington after Congress' long July 4 recess.

The freshmen also reported that, even where the recession is rapidly receding, there are fears that huge budget deficits are contributing to a surge in interest rates that could again stall the economy.

Concern about military escalation and budget deficits combine to produce an almost universal demand for restraint in Reagan's military buildup.

The freshmen's findings also underscore the uneven nature of the recovery, which has brought boom times to some areas while leaving others virtually untouched, producing conflicting priorities even among geographically close districts.

The freshmen, representing districts ranging from California's Silicon Valley to Pennsylvania's depressed steel towns, were chosen for interviews because many represent swing districts and most have remained close to the home folks in their first six months in office.

If the first-termers are indicative of Congress as a whole, the rest of 1983 on Capitol Hill is likely to be especially unsettled, posing problems not only for the administration but also for those who try to maintain discipline within Congress.

Moreover, foreign policy, slow to emerge as an issue in Reagan administration dealings with Congress, appears likely to be a major source of contention in next year's election campaigns.

On the surface, the president appears to have regained at least some of the strength he lost in the depths of the recession, with his popularity tending to match the degree of economic recovery.

In New Jersey's largely affluent Bergen County, Robert G. Torricelli (D-N.J.) has found that a rebounding economy "has stabilized the situation for the president politically," although Torricelli said Reagan receives only partial credit for the recovery, just as he received only partial blame for the recession.

In the Dallas-Fort Worth area, coming back strongly from a relatively light brush with the recession, Tommy J. Vandergriff (D-Tex.) sees Reagan gaining in popularity, although he is "not nearly as strong" as in 1980.

"Generally, people think he's trying," and the climate for Republicans is much better than last year, said Thomas F. Lewis (R-Fla.).

In Seattle's white-collar suburbs, "the mood is really upbeat, with a few glitches," said Rod D. Chandler (R-Wash.), who added that one "glitch" is Interior Secretary James G. Watt.

But in the hard-hit southwestern tip of Virginia and rural northern reaches of New Mexico, where the recession lingers, Frederick C. Boucher (D-Va.) and William B. Richardson (D-N.M.) found that Reagan has recovered no better than the local economies.

In his half-rural, half-industrial district, Lindsay Thomas (D-Ga.) finds that bankers are "fairly optimistic" and home builders hopeful though nervous about the long-term outlook. As for blue-collar workers, "they're the most concerned . . . ; they're really pessimistic," he said.

The uneven hand of economic recovery and resulting disparity in voter concerns is probably best illustrated by districts represented by Edwin V.W. Zschau (R-Calif.) and Thomas J. Ridge (R-Pa.).

In the booming computer-land of California, "It's hard to get anyone to even talk about the economy . . . . It's a problem that people think they've put behind them," Zschau said.

In fact, "It's hard to get them to talk about anything other than foreign policy, especially Latin America and arms control," he said. The most organized and vocal are those critical of the administration's policies, he said, although opinion spans a broad spectrum, including those who believe "we shouldn't even be talking to the Soviet Union" on arms control.

In Ridge's northwest corner of Pennsylvania, where unemployment is pushing 18 percent, higher than when he was elected last November, Central America came up only once or twice in a half-dozen town meetings held by Ridge during the recess. "It's the same everywhere," he said, "jobs, taxes, the economy."

But if the economy has crowded out foreign policy in the most depressed smokestack towns, concern about the administration's hard line on arms control and its military involvement in Central America has percolated to the top in many other districts.

Among the lawmakers interviewed, most said their constituents had serious misgivings, at the least, about military aid to El Salvador and covert assistance to antigovernment rebels in Nicaragua.

Some said their constitutents supported Reagan's policies in Central America but, as Vandergriff put it, would prefer to "confine our presence to a political and economic presence."

Said Nancy L. Johnson (R-Conn.): "People don't disagree with the president that Central America is important to us, but they feel we should be seeking alternative solutions."

"The parallel with Vietnam is just too strong," Alan D. Wheat (D-Mo.) said.

"I don't think I've found one citizen at 31 town meetings held over 10 days that supports the president in El Salvador," New Mexico's Richardson said.

"People just don't see spending so much on El Salvador when it's needed here at home," said Bob Carr (D-Mich.), whose Pontiac-area district still suffers from 30 percent unemployment.

"People ask who are the good guys, who are the bad guys and which side are we on," Gerry E. Sikorski (D-Minn.) said.

"Even conservatives aren't buying the anti-communist line," Peter H. Kostmayer (D-Pa.) said.

Passions also run high over arms control, although perhaps less pervasively.

Washington's Chandler, who voted for the MX missile on the first go-round, was told by his constituents they felt "betrayed" by the administration's subsequent positions on arms control. "Frankly, I felt betrayed, too . . . ," said Chandler, who said he has not decided how he will vote on the MX next time.

At a town meeting with nuclear scientists at Los Alamos, Richardson reported, the vote was 14 to 2 to support his stand against the MX missile.

Several freshmen said skepticism about defense spending was fueled by concern over deficits and their potential impact on interest rates, which, in turn, tended to temper optimism about the recovery.

"People think we're in a recovery, but they're concerned about how long it will last," said Richard H. Lehman (D-Calif.), whose San Joaquin Valley district still has unemployment of about 17 percent. "People have a hard time figuring how inflation is 3 percent and interest rates are 12."

From Lewis' prosperous district to Ridge's recession-wracked one, tax increases had no appeal. Vandergriff said he heard some willingness to accept tax increases only if revenue is used to reduce deficits, not boost spending.