Does President Reagan want to earn the nickname President Roadblock? Does he really want to create the impression that everybody's out of step but Ronnie?

These questions arise because, at a time when lawmakers of both parties are exhibiting unusual concern and cooperation in addressing some of the nation's major problems, the president is becoming the chief barrier to action.

The latest incidents, just last week, saw Reagan denounce the budget produced by the Democratic majority of the House Budget Committee and intervene to delay a vote on a similar measure in the Republican-controlled Senate Budget Committee. His aides make it clear that he will continue to oppose the bipartisan effort in Congress to discipline defense spending as part of an overall strategy for reducing the future deficits everyone regards as the main threat to economic recovery.

This is the same president who whipped Congress into a lather his first months in office, lashing the legislators to write his basic economic program into the statutes.

Six months after he was elected, three months after he submitted his first budget-and- tax package in 1981, Reagan came before Congress and said, "The American people now want us to act, and not in half measures. They demand, and they have earned, a full and comprehensive effort to clean up our economic mess."

But two years later, with the "economic mess" at least as great, the same Ronald Reagan has turned into a disciple of delay.

Reagan leaned hard on Budget Committee Chairman Pete Domenici (R-N.M.) to postpone action on the budget for three weeks. He did so in the knowledge that a bipartisan majority of about 16 of the committee's 22 members was ready to endorse a 5 percent increase in real defense spending--just half as much as he has asked for the 1984 installment of his accelerated military buildup.

Rather than let that happen, Reagan, with the help of Senate Majority Leader Howard Baker, invoked the reluctant Domenici's party loyalty to call off further work on the budget. The administration will use the hiatus for one more effort to persuade and pressure the Senate to give Reagan what he wants. The centerpiece will be a March 30 defense speech by the president himself; but every senior official will be turned loose to lobby for Reagan's plan to add almost another $100 million a day to a defense budget that will, if he has his way, reach the $1 billion-a-day level within two years.

In the view of Senate Budget Committee Member Slade Gorton (R-Wash.) and other Republicans I talked to, Reagan's intervention "diminishes the chances for a bipartisan agreement" on a package of spending cuts designed to reduce the prospects of near-permanent deficits of more than $100 billion a year.

Domenici has been seeking to persuade both Democrats and Republicans in the Senate to accept a painful but balanced program to whittle away at the horrendous deficits. It asks Republicans and defense-minded Democrats to accept a slowdown or stretchout of the military buildup; not reduced defense, but less frantic acceleration. In return, it asks Democrats and liberal Republicans to swallow a needed but painful slowdown in Social Security and Medicare and other entitlement spending.

The key to the strategy's success is to keep it in balance. But, as Gorton said, "the president is so focused on defense, he's forgetting we're working on the whole package." That is more than forgetfulness, however. It is an intervention in the congressional budget process that wreaks havoc with what has been and remains the country's best hope for vitally needed long- term fiscal discipline.

As another Budget Committee Republican source, who insisted on anonymity, told me, "There's much more at stake here than a three- week delay. We were on our way to developing an atmosphere where a majority of the committee on both sides would have a stake in the resolution. I'm not sure that will survive the delay. I think the president's tactic is likely to polarize things here, and the process will be severely damaged."

This is not the first time Reagan has thrown a monkey wrench into the congressional budget process--a process that he foolishly denigrated back in 1981 as "a kind of Rube Goldberg thing that doesn't make . . . much sense."

In 1982, when his original budget met a stone wall of deserved skepticism from lawmakers of both parties, Reagan did not let Congress get about its work. Instead, he drew House and Senate budget-makers into five weeks of futile negotiations with his administration representatives that yielded nothing. Thrown off schedule, Congress spent most of the year squabbling about budget issues.

Now he is threatening the same kind of slowdown. The congressional budget process provides a chance for spending restraint and perhaps economic recovery. If he can't lead it, at least Ronald Reagan shouldn't wreck it.