Not exactly by popular demand, understand, but this city's sweetest attraction, Fun and Games (legislative style), returned to Capitol Hill yesterday for a fall run.

Which is to say that Congress came back to work, sort of, after a month of vacation, to confront a calendar laden with such pressing matters as energy, inflation, strategic arms and the like.

Both the House and the Senate were in session, but the confrontation was skillfully avoided. The House spent most of the day debating foreign aid (a few members even showed up), and the Senate labored over a Treasury-Postal Service appropriation bill.

There is such a thing as peaking too soon, of course, and for starters at least, Congress was having none of that on its first day back.

Today, however, it could be a little different, and energy issues will be among the first orders of business.

House and Senate committees will continue work on President Carter's proposal to create an energy mobilization board to speed up projects vital to the country.

And on Friday, House-Senate conferees are scheduled to meet to try to work out differences in a gasoline rationing bill avidly sought by the White House.

On that note, House Speaker Thomas P. (Tip) O'Neill Jr. (D-Mass.) said that, during the Democratic leadership meeting yesterday with Carter, he had asked the president to dispatch more liaison people -- that is, lobbyists -- to Capitol Hill to push the White House position.

For his part, O'Neill said, he intended to spend the rest of this week sounding out House members, particularly freshmen, to get a better feeling on energy legislation in general and prospects for passage.

A month at home in his district, O'Neill said, was enough to convince him that his constituents want more congressional cooperation with Carter and more congressional action on energy.

The first meaningful legislative act yesterday occurred before noon in the Senate. Sen. Thomas F. Eagleton (D-Mo.) got his colleagues to adopt a resolution commending St. Louis Cardinal outfielder Lou Brock for his contributions to baseball.

Moments before, Sen. Richard G. Lugar (R-Ind.) had eulogized the late senator Homer E. Capehart (R-Ind.), who died this week, as a patriot, farmer and champion jukebox salesman.

Lugar noted that Capehart, who served three terms between 1944 and 1966, would have gloried in the debate that had just occurred.

The debate, such as it was, consisted of Majority Leader Robert C. Byrd (D-W. Va.) saying that Senate consideration of SALT II ought to go on independent of the U.S. response to the disclosure that the Soviet Union has combat troops in Cuba.

Minority Leader Howard H. Baker Jr. (R-Tenn.) took the opposite view -- that SALT must be considered in light of Cubans in Africa and Soviets in Cuba. He said the Soviets are "thumbing their noses at us" by having a combat unit in Cuba.

Rather heavy stuff, that, so sit back and enjoy the Fun and Games (legislative style).

Here we have Rep. Bill Frenzel (R-Minn.) reporting that people at home talk to him a lot about what is called the Billion-Dollar Congress.

Ehough is enough, by gum, he told the House Select Committee on Committees. So he urged approval of a resolution to prevent members from hiring a special staff assistant for each of their committee assignments.

Rep. Jerry M. Patterson (D-Calif.), the chairman, was saying the same thing, that the staff hiring situation has gotten out of hand, but the committee wouldn't bit the old bullet.

The committee decided to talk about it later this month, but Frenzel lost another big one to Patterson. The committee voted 6 to 4 to recommend construction of a new little hideaway near the floor for members.

This work space would be in the historic gallery of Statuary Hall, the first House chamber in the older section of the Capitol.

Patterson and his allies thought it a dandy idea. There would be 42 telephone and work cubicles and 396 lockboxes, all available on a first-come, first-served basis, meaning some among the 435 members would be losers.

Frenzel, and Reps. Butler Derrick (D-S.C.) and Patricia Schroeder (D-Colo.) worried that the hideaway would intrude on the storied nature of the splendid little chamber and its small rotunda. No way, said Patterson, it all would be hidden from public view behind a wall.

Next step: the recommendation goes to the House Office Building Commission for a vote.

There was another little committee meeting yesterday -- the speaker's special panel to decide what steps, if any, to take to curb grandstanders who are monopolizing television time in the House.

O'Neill had been worried that some members were simply talking too much since the House went nationwide on cable TV.

Rep. Charles Rose (D-N.C.) head of the special panel, counseled: "The people can spot obstructionism and grandstanding . . . We feel the system does not need drastic surgery. The patient is well. He may need a sedative, but not surgery."

Rose and his committee, after their session with O'Neill, said they will continue their efforts to dissuade the speaker from turning down the lights.

Pass the Valium.