All his life, Washington's Walter Weiner wanted to be a comic. In school he was always the cutup in the the back row. Even his first job, at 15, after school, was funny: delivery boy for a tuxedo rental. ("Delivering wasn't so bad, but picking 'em up was another thing. They were on their honeymoon and you'd bang on the door and bang on the door . . .") At 17 he tried to sell gags to comedians, but he had no luck even though he was from Boroklyn. He married young, had two children and after awhile found himself in the insurance business.

Shortly after he turned 50, he got a sruprise.

"I've had my name on the door of my office for years. When i came in the other morning, my name was written on the door in chalk only, and a wet sponge was sitting on the door knob. Since there are only two of us in the office, I think my son was trying to tell me something."

The passage is from his book, "So Call It a Mitzvah," 101 pages long and printed by a vanity press. It's not everyone who gets his Big Break from his son.

Weiner insists he hasn't dropped out. He's just starting a new career. It's the thing to do, these days, though one suspects that most former class clowns at 50 have long since given up yearning to recapture that particular form of glory.

Weiner has tried his act before clubs and lodges, and the big hotels in the Catskills pay his expenses for throwing some chuckles into the guests at poolside between the headline acts.

Last summer, for instance, he spent a week in the mountains, hitting two top hotels each day. The Concord even asked him back for s second time in the Jewish holidays.

"I'd stand around the pool and hold up my book and start talking about my adventures in trying to market it, and pretty soon they'd be asking questions. It seems everyone is writing a book or knows someone who is. So we talked about the publishing business for 45 minutes."

Sometimes he would talk about his early jobs, like the time he drove a bus between New York and Washington, and how passengers would get on in New York with a ticket to Newark and try to go all the way. He had to throw them off, whatever blandishments they offered.

The material is what you would call uneven.

"When I was 4 years old, I remember the picture I took sitting on a pony. My mother sent the picture to Hollywood, but they said that all they could use was the pony in a cowboy picture. Well, the horse went to Hollywood, and i stayed in Brooklyn . . ."

At junior high, he even flunked shop."Well, they had to find something for me to do, so they put me at the front door of the school, and I had to open the ddoor for the teachers and principals when they came and went each day. Not only did I not have a uniform, I never got one lousy tip the whole time I had the job. They could have at least given me a piece of chalk."

It always seems to go one sentence too long.

"Basically, I always wanted to write for someone else," Weiner says. "I cut class every time Jack Benny was in town. My highest grade was in cutting classes."

Ever since he and Sid Caesar tried out for the Coast Guard "Tars and Spars" revue, and Caesar went on to fame with his saxophone tunes and imitations of German planes while Weiner won an assignment to the South Pacific, he has felt bypassed.

He sent stuff to Jan Murray, Dick Shawn, Don Rickles. Nothing happened. He wrote comic raosts for the Masonic lodge he belongs to in Washington, he spoke before the B'nai B'rith, he practiced routines before the shaving mirror where he gets his inspiration.

Finally, two years ago, unshackled by his son, he wrote his book. After rejections by several agents, he decided that since selling was his business he should get the book printed first and then promote it. Certainly the publisher, with a $420 promotion budget, wasn't going to make him a best-seller.

"The title was my son's idea," he says. "I couldn't think what to call it, and he said, 'So call it a blessing,' which is mitzvah."

Better he should have said chutzpah. Surely no subisdy press book was ever pushed like this one. Weiner has taken it into more bookstores than he can remember, and only a few have refused, mostly because of policy. He's had reviews in some Jewish newspapers and local journals. He even showed up at the Press Club book fair to sign copies, hobnobbing with Art Buchwald.

He has also hired a public relations firm to get him national exposure.

"I've finished my second book already and i'm working on a third."

Then there is the column he plans to write for a Philadelphia paper starting in January. "It's gradually picking up," he says, "gaining momentum."

His humor mostly draws on his own experiences, ranging from his circumcision ("There I was crying, and everyone was drinking wine and eating sponge cake") to his new career ("I just made my first trip to a book publisher's office. The young lady at the desk said take a number . . ."), ad the references are the ones made familiar to all of us by Benny, Mel Brooks, Carl Reiner, Allan Sherman and other Jewish comedians.

It is the humor of trigger words: Ovaltine, prunes, training bras, Miami Beach, clevage, bagels, Brooklyn, vaseline and the cruise ship where his stateroom was so far down he looked out the porthole and saw the fish alughing at him.

It is the humor of the 50-year-old, balding, wrinkled, divorced and worried.

"Boy, did I meet up with an old established firm. Experience she has. She teaches sex at Weight Watchers. She said that I could eat all I want to , and all I would have to do is have sex three times a day, and I would burn up all calories and carbohydrates. She is correct. She weighed me before we started and after we finished and I lost three pounds. The only trouble with that is that I burned up my strength too. Well I lost three pounds anyway."

His nex book is about the first vice president from Brooklyn, described as a satirical novel. He has high hopes for it.

"It's luck, you gotta have that lucky star. I met a lot of comics on the Borscht circuit, and they were very talented, they had just as much talent as Jack Carson or Don Rickles. But they never quite made it."