The sellout crowd of 2,000 was getting restless, but then that old familiar voice pulled them in with the jokes and the well-articulated assaults on that always easy target - Big Government: "Government is getting more like that old definition of a baby - an alimentary canal with an appetite at one end and no sense of responsibility at the other."

Ronald Reagan - Hollywood's Grand Old Man of the Grand Old Party - is ignoring the fact that he's between seasons. Once again, he's going around the country as if he's running for office.

And Reagan - California's former governor and the conservative who in 1976 came as close as anyone in history to wresting the nomination from an incumbent President - is finding a broader audience these days to applaud Vintage Reagan.

The past four days have been like a mini-campaign for Reagan: Boston, new York, Baltimore, Washington. Press conferences and parties, speeches and signing autographs, best wishes and cheers, the inevitable, "Will you run in 1980?" a question guaranted to fall like Christmas Carols on the ears of any politician.

Reagan has been in 75 cities this year.With him are the familiar aides - coat carriers, crowd pushers, the nudgers who wrest politicians out of the hands of interviewers and on to the next stage.

Wednesday night, following a speech at Towson State University, students, faculty and guests shoved into a crowded steamy reception to meet Reagan, who held an empty champagne glass, talked to all who could get near him and, in that practiced way of politicians ignored the aide who signaled, wigwaved, then finally shouted to another, "We'll take him down the back stairs!" In one gliding movement, they flanked Reagan, moved him out and when a gurst turned back to talk to Reagan he was gone.

It takes years of practice to make it all go as smoothly as Reagan does.

Reagan, taller than one expects, is in fact as smooth and neatly packaged as his oratory. His smile is pleasant, at once familiar and studied. He looks ready to go on stage at all times - slicked-black hair, brown suit, cuff links, elephant stick pin in his rust tie. But then he takes a half hour to change into a crisply creased black suit and white shirt. Reagen once remarked when he saw one of his old movies, such as "Knute Rockne - All American," "It's like looking at a younger son I never knew I had." There are still remnanta of that long-ago actor in a face that is remarkably ruddy and creaseless.

He looks very sincere when asked about running in 1980. In a Towson, Md., Quality Inn motel suite, Reagan sits between preformances and says, "That's up to the people," What about being too old? He smiles again. "That's up to the people to decide." tr for ad 3

Reagan, who will be 67 in February, is one of the few presidential candidates who has had to apologize for looking young. No, he never had the facelife other politicians insist he's had. He ducks his head under a light to show the few strands of gray among the rust-brown, a strange ritual, but then no one else has ever been called the politician with the "prematurely orange hair." It's genes not dye, he says, and recalls the time some California reporters took snips of his hair from a barber to see if it was dyed. It wasn't.

Still, odds are against Reagan on age alone. In 1980, he would be a year older than our oldest President, William Henry Harrison, who was 68 when he took office in March of 1841. Harrison caught cold during his inaugural and died the next month. But then you listen to Reagan . . .

"The barons of Bureaucracy have forgotten we are their employers . . . when you get in bed with the government - you're going to get more than a good night's sleep!"

They were on the edge of their seats now, the crowd at Towson State's lecture series.

These were not politicos or Reaganites, for the most part, but mostly the well-to-do and middle-aged who attend the lecture series. Reagan was the largest draw this year. Truman Capote, who was, to put it gently, helped off the stage by student aides as he started an incomprehensible monologue a few weeks ago, didn't attract that many. Neither did former Israeli Foreign Minister Abba Eban.

Reagan earned $5,500 and expenses for a speech and Q-and-A session that lasted a total of one hour. With businessman predicting recessions and polls tracing a conservative trend. Reagan's absoluteness and simple solutions strike a responsive chord and reassure - in the classic way that George Wallace did, and even Jimmy Carter did not so long ago when he was railing against government waste.

Larry Lisker, a 33-year-old book salesman, said, "this crowd is at least half Jewish, well-to-do, middle-class, which is what I am. Reagan strikes home one things like less government meddling." There are Republicans and Carter Democrats, and some Democrats who had voted for Ford in 1976. There was a retired black waiter, schoolteacher, a C.P.A., sitting next to one another. The accountant voted for Carter, but would vote for Regan over Carter if there were an election tomorrow. "I'm disappointed in Carter - particularly on things like Social Security."

A few minutes later the crowd roared approval as Reagan talked about Social Security. "The President's gigantic tax, if passed, will triple the tax for everyone - employer and employee alike. Young people, if they had the same money in their hands, could buy a private insurance policy that would offer them more than double what they could get from Social Security. Just increasing taxes is only going to stave off disaster a few years."

He swamps audiences with statistics, old jokes, anecdotes and flag-waving patriotism.

Reagan describes how one school's dietary standards were turned over to fast food and free enterprise. "When an Arkansas hot lunch program was failing, a disgusted school board had a talk with McDonald's and they set up shop in the school cafeteria. Now 10 times as many kids are eating there, McDonald's is making a profit and the school board is saving the taxpayers $1,000 a month."

Finally, he talks of an Idoho businessman who defied Occupational Safety and Health Administration inspectors: "I love the old boy's answer. He said, 'We sent our young men to fight and die for freedom. Maybe it's time us old dffers did something.'" Reagan lowers his voice as the applause comes . . . "And so he fought. "

Reagan, who listed his net worth at nearly $1 million in 1978, says he needs the money from his lectures, radio show and newspaper column

"I have to make a living. I really do! The Democratic legislature changed the pension laws so I get half or less than what other California ex-governors get."

Reagan releaxes by riding horses off on his ranch with his wife, Nancy, every 10 days or so, but he admits that the old mashed potatoes circuit revitalized him. On the road, he is absorbed by politics.

"Has Carter done anything right? I can't think of anything. I'm asked if he'll be a one-term President. If he keeps on the present way . . . but I remember a fella named Truman who at the same stage in office was vastly hated. So who knows? They read those polls at the White House, too."