A new presidential task force was born yesterday, taking its place in a Washington landscape littered with dead and dying commissions, boards and task forces of earlier administrations.

The new Presidential Task Force on Private Sector Initiatives is designed to stimulate voluntarism, President Reagan announced. In other words, the president who promised to get government off the backs of the people, has established a 35-member task force to help do that job.

"Voluntarism is an essential part of our plan to give the government back to the people," Reagan said in a speech to the National Alliance of Business at the Sheraton Washington Hotel.

In announcing the task force chaired by C. William Verity, chairman of Armco Inc., Reagan took another step that seemed slightly at cross-purposes with his desire to shrink government. He suggested that government has a role in stimulating private sector activity.

"I am also asking the Cabinet to develop pump-priming and seed money programs that offer incentives for private sector investment," Reagan said. "In addition, the Cabinet will provide technical knowledge to develop private incentives," the president said.

The speech was the latest in a series of Reagan exhortations for voluntary action to pick up slack caused by the cutbacks of many federal programs. The president is well aware that some people doubt such a plan will work.

"They believe voluntarism is a mushy idea and the product of mushy thinking. They say our society today is too complex or that we are trying to repeal the 20th Century. The cynics who say these things have been so busy increasing Washington's power that they have lost sight of America," he said.

Reagan ended his speech: "Let us go forth from this conference and say to the people: join us in helping Americans help each other."

Then the president paused before ad-libbing to let his business audience know that he doesn't have any doubts about them: "I feel like I'm preaching to the converted or saving souls in heaven."