After 2 years of quiet retirement, 72-year-old Samuel Greenberg is trying to enter history books as the first write-in candidate to become governor at Virginia.

Undaunted by the million-dollar campaingns of Republican John-Dalton and Democrat Henry E. Howell, Greenberg, a retired Army colonel, is touring 20 cities this month, surprising would-be voters and Virginia politicians by announcing that he is a serious, if somewhat unorthodox, politician.

"Somebody's got to do it," he tells voters when asked why he is running in a state where election officials are at a loss to recall a write-in candidate who has won a statewide race. "The smaller the number of voters, like in a town, the better are the chances" for write-in, said Joan S. Mahan, state elections board secretary.

Money, which Greenberg doesn't have, which his two opponents do, may turn out to be the deciding issue of the race, Greenberg said the other day as he sank into a reclining chair in his 78-year-old whit clapboard house at the corner of Washington Boulevard and Roosevelt Street in Arlington."I feel that in the next two months people will begin comparing my spending with theirs and they will begin to come over to support me," he said.

Greenberg, who supports himself and his wife on a $1,600 a mont military pension, has pledged to spend amount that he concedes may be low because of the high costs of campaigning in Virginia.

"I'm not a believer in spending, he said. So, he limited himself to the purchase of 40 green-and-white campaign buttons (at $1 each) and 125 bumper stickers (at 60 cents each).

Despite the two buttons he wears and the one bumper sticker on his gray 1969 Chevrolet Caprice, the name Greenberg is not yet exactly a household word in Virginia. "I don't think I know the man," said Howell. Democratic nominee for governor, during an Arlington campaign swing last week.

"Sam Greenberg? Sam Greenberg?" asking Republican Dalton's press secretary Richard Lobb. "Well," he added when told of Greenberg's first political campaign, "it's a free country and anybody can run."

In Virginia, there are no rules on write-in candidates, are supposed to file a sworn statement of their expenditures. That should be a relatively easy task for Greenberg. No one has offered him money, he said the other day, and, if they did he says, "I'd send 'em back."

Political giving and campaign organizations are two of the things that corrupt the election process, and "I don't care for that kind of campaign," he said.

Greenberg concentrates instead on patiently turning out press releases he types at home and reproduces at a neighborhood shopping center. His campaign stops, like those he is making this week in Farmville, Stewart and Charlottesville, feature a speech before the local governing body, a stroll over to the local newspaper to request an interview and a visit to the local radio station "if they have one" to ask for another interview.