The trial of John W. Hinckley Jr., who is accused of the attempted assassination of President Reagan, was rescheduled in U.S. District Court yesterday for Jan. 4.

The trial had been set to begin Nov. 30 and was expected to take at least five weeks to complete. Yesterday, however, Judge Barrington D. Parker told prosecution and defense lawyers that he had decided to reset the trial date after considering the impact on the jurors if the case overlapped with the upcoming holidays.

Hinckley has admitted that he shot Reagan and three others outside the Washington Hilton last March 30. His defense lawyers have told the court that they plan to argue at the trial that Hinckley was insane at the time of the shooting and thus should not be held criminally responsible for his acts. Hinckley currently is being held in the Army stockade at Ft. Meade, Md.

Parker told the lawyers that he has not yet decided whether or not the jurors in the case should be sequestered during the trial to avoid exposing them to the widespread publicity that is expected once the proceedings begin.

U.S. Attorney Charles F.C. Ruff, who has been handling the Hinckley prosecution with Assistant U.S. Attorney Roger M. Adelman, told Parker yesterday that the Jan. 4 trial date may require him to "step out" of active involvement in the case. The Reagan administration has nominated D.C. Court of Appeals Judge Stanley S. Harris to take over the top prosecutor's job from Ruff, who was appointed by former President Jimmy Carter. Most observers expect Harris will be sworn in as U.S. Attorney by the start of the new year.