Calling themselves just "two ordinary people," Greek shipping heiress Christina Onassis and her new Russian husband spent their first day of married life yesterday puttering around their two-room Moscow apartment and preparing for a Siberian honeymoon.

Reached by telephone at his mother's apartment - the couple's "home until they can find rooms of their own" - Sergei Kauzov, 37, echoed his wife's wish that they be allowed to fade into the obscurity of a quiet domistic life she has never known.

"I don't know why reporters want to find out something sensational about Christina and myself," said Kauzov, an unemployed former official of a Soviet shipping firm. "We are two ordinary people."

The Soviet press - which attended the wedding Tuesday while western reporters were barred - continued to give the newlyweds the anonymity they requested: not a word has been printed about the marriage of the capitalist millionaire and the Communist Party member she met in Paris.

Kauzov said he and his wife would leave today for a honeymoon at picturesque Lake Baikal and Magaden in Siberia "to relax a bit."

If the weather there is poor he said, his wife wants to head farther east or north into the Siberian hinterlands.

Magadan is off-limits to foreigners and Kauzov had to arrange for special permission to take Onassis there.

The town is known, among other things, for the number of Soviet prison camps scattered around it.