The Reagan administration has begun to pick people for the second-and third-level economic policy jobs throughout the government but as of yesterday still had not settled on anyone for chairman of the Council of Economic Advisers.

The failure to fill the CEA position, even though new economic policy proposals will be the first order of business for the incoming administration, has led to increasing speculation that the chairman will not be expected to play a major policy role.

The name of Murray Weidenbaum, an economist at Washington University in St. Louis, is said to be at the head of the list of possible CEA chairmen.

Three other economists have been picked as key undersecretaries, two at the Treasury Department and one at the State Department:

Beryl W. Sprinkel, 57, executive vice president of Harris Trust and Savings Bank of Chicago, will be undersecretary for monetary affairs at Treasury. Sprinkel, a monetarist in the Milton Friedman tradition, will oversee both domestic and international monetary matters, including management and financing of the federal debt.

Norman B. Ture, a Washington consultant who has specialized in research in taxation, will fill a newly created post of undersecretary at Treasury, probably with both the assistant secretaries for tax policy and for economic policy reporting to him, sources said. Ture, representing business clients, frequently has testified at congressional hearings in favor of business tax cuts and added tax incentives for investment.

Myer Rashish, 56, also an economic consultant in Washington, will become the undersecretary of State for economic and business affairs. Rashish is chairman of the Advisory Committee on Trade Negotiations, a private advisory group to the Carter administration's cabinet-level trade negotiator. A former Democrat, he has had long experience in Washington dealing with trade matters.

In a marked departure from other Reagan selections, a Carter administration official, Robert Hormats, the acting trade negotiator, has been chosen to work with Rashish as the assistant secretary of State for economic and business affairs.

Hormats, also an economist, was on the National Security Council staff in the Nixon administration when General Alexander Haig, the incoming secretary of State, was its deputy director. He later was a deputy assistant secretary at State before moving to the trade negotiator's office. Hormats, as official note-taker, is the only official to have attended all six of the annual economic summit meetings among the heads of government of the United States, West Germany, France, Canada, Japan, Italy and the United Kingdom.

Paul Craig Roberts, an economist with the Institute of Policy Studies at Georgetown University, may be named as assistant secretary of Treasury for economic policy, sources said.

Roberts, a monetarist, while working as a congressional assistant and teaching at George Mason University in Northern Virginia had a major role in developing and popularizing the tax-cut proposals that lie at the heart of the so-called supply-side economics. He was particularly influential in persuading Rep. Jack Kemp (R-N.Y.) to back what has become the key element of Reagan's economic policy proposals.

Sprinkel, who has been with Harris Bank since getting his Ph.D. from the University of Chicago in 1952, is a devoted free-market adherent who believes no attempt should be made to manipulate exchange rates. One fellow economist who knows him well declared, "If they want a monetarist economist who knows money markets and can't be pushed around," Sprinkel is their man.

Ture, also a University of Chicago Ph.D., has taught public finance theory at the Wharton School of Finance and at George Washington University. He worked in the Office of Tax Analysis at Treasury from 1951 to 1955 and was on the Joint Economic Committee staff from then until 1961.

Rashish, who has a Ph.D. from Harvard University, first served in the State Department in 1961 as an assistant to George Ball and then as a White House aide in the Kennedy administration.