The Western-sponsored attempt to save the United Nations' plan for Namibia's independence got off to a shaky start today because of South Africa's anger at the simultaneous scheduling of a Security Council debate on condemning recent South African raids against Angola.

As a result, Secretary of State Cyrus R. Vance and other Western officials, who came here in hopes of breaking the impasse in the move toward independence, were forced to wait for hours while South African Foreign Minister Pik Botha concentrated on the council debate.

Late in the day, the so-called "proximity talks," with the United States and four allies trying to mediate between the contesting factions in the Namibia dispute, did get under way. But, diplomatic sources said that because of the delay, the talks might take longer than the two days originally set aside.

At issue is the fragile two-year effort to create an independent Namibia out of Southwest Africa -- a sparsely populated, but mineral-rich territory dominated by South Africa for 60 years under an old League of Nations mandate.

Last July, the Security Council approved a plan for U.N.-supervised elections to give the predominantly black populace its freedom from white-dominated South Africa. But the plan since has been Jeopardized by continuing warfare between South Africa and the guerrillas of the Southwest Africa People's Organization (SWAPO), which Pretoria regards as communist-controlled.

That led South Africa to threaten a pullout from the U.N. plan and to launch attacks two weeks ago on SWAPO bases in neighboring Zambia and Angola. These raids prompted the Security Council debate that saw much of today's negotiating time drain away as delegates from black Africa and their supporters denounced South Africa.

After spending hours in seclusion, reportedly debating whether to reply in person, Botha finally sent a letter to the council charging that the meeting was an attempt to undermine the proximity talks, which were scheduled outside formal U.N. auspices. He said any condemnation should be directed against SWAPO

Tonight. Botha began discussions with Vance. U.S. diplomats played the leading role in working out the Namibia agreement and as recently as Saturday, Vance cited it as a model for the peaceful solution of the racial conflict in Rhodesia.

If the negotiations here fail, the guerrilla warfare could escalate as black African countries are drawn into more direct military support of SWAPO. The United States and its allies also would come under intensified pressure from black Africa to apply economic sanctions against South Africa.

South Africa has complained that U.N. officials, in planning the elections, want to allow SWAPO to establish bases inside Namibia and have failed to make provision for monitoring SWAPO forces in neighboring countries. As a result, South Africa contends, SWAPO will be able to use its military power to intimidate voters and influence the elections.

Some observers here believe the South African government, beset at home by a political scandal, is trying to divert attention by taking a tough line on Namibia and could back out of the agreement.

South African sources here insisted today that they do not want to close the door to the U.N. plan or put their country in a position of confrontation with the United Nations or the United States and its allies.

These sources added, however, that the Pretoria government is adamant that SWAPO Lot gain an unfair advantage over the other Namibian political groups seeking to win power in the elections and will insist on approval of these groups.