John W. Hinckley Jr.'s mental problems were no more severe than the depression experienced by some air traffic controllers or the narcissism of Hollywood actors, a prosecution psychiatrist testified yesterday.

On the day he shot President Reagan, Hinckley was in control of his behavior and able to abide by the law, Dr. Park Elliott Dietz told the jury. He said in 25 hours of interviews with Hinckley he observed symptoms of a number of common mental problems, but added:

"There are many, many people functioning in any city on any day who have these personality disorders."

Dietz' testimony came in stark contrast to the testimony of four experts for the defense, who said Hinckley suffered from forms of schizophrenia, a serious mental illness marked by withdrawal from reality and by deep depressions.

As yesterday's session opened, Hinckley offered a public apology for leaving the courtroom several times during the proceedings, most recently Thursday.

"I felt bad about what I had done because my attorneys and my mother pointed out to me that it was not a very good thing to do, getting up and leaving whenever I wanted to, and I see their point," Hinckley told Judge Barrington Parker. Hinckley's mother and father have attended each day of the trial.

Dietz, the first psychiatrist to testify for the prosecution, told the jury that 1 out of every 10 to 20 Americans, from writers to air traffic controllers, experience the "down in the dumps" symptoms of one mental disorder he saw in Hinckley, which Dietz said is generally described as a "bad mood."

He said Hinckley also had features of a "narcissistic personality disorder" commonly seen in actors, athletes, doctors and academics. Such a vain and self-centered view of one's own importance "is what Hollywood is about," Dietz told the jury.

Hinckley also demonstrated a "schizoid personality disorder" seen in persons who do "loner sorts of things" and who are drawn to jobs that require limited interaction with people, like cowboys, computer operators, librarians and forest rangers, Dietz testified.

Dietz, an assistant professor of psychiatry at the Harvard Medical School, told the jury that Hinckley exhibited features of other mixed personality disorders that could not be put in a single category, such as dawdling, boredom and resistance to demands to get a job.

He flatly contradicted the defense contention that Hinckley was legally insane, testifying that Hinckley was not psychotic, or out of touch with reality, when he wounded Reagan and three others.

Hinckley, visibly restless when Dietz began his testimony yesterday, later appeared amused by some of the psychiatrist's statements, whispering remarks to his defense lawyer beside him.

Earlier he had told Parker he left the court Thursday because "I just got very edgy sitting there at the defense table . . . There is just times when I get edgy because of thoughts that are going on in my head . . . I can't help it."

"You better get this clearly implanted in your mind, that you don't get up and leave when you want to," the judge responded. "That is not the way this court is run. . . . "

Hinckley assured Parker he planned to stay but added: "I cannot swear to you I will sit there like a stone for the rest of the trial. I just can't do that to you, but all I can say is that I will try my best to sit there."

Parker said it appeared to him that Hinckley became restless when critical testimony put Hinckley "in a light that perhaps you don't like to hear." With prosecution witnesses in the stand, Parker warned him, "You are going to hear a lot of testimony like that and you may not like it."

Hinckley's last exit came during prosecution testimony about brain scans performed on him, but he said yesterday "that was not bothering me." As Hinckley was about to explain what was bothering him, defense lawyer Vincent J. Fuller interrupted and told Parker he felt his client had said enough. Hinckley, his face flushed, resumed his seat at the defense table.

Dietz told the jury there was "little to suggest" that Hinckley was seriously depressed on the day he shot Reagan except for Hinckley's own statements that he had considered suicide and had difficulty sleeping. Dietz said Hinckley had a mood disturbance, called "dysthymic disorder," which Dietz said translates for Hinckley into "sad mood."

Hinckley showed that disorder by weight gain, loss of energy and sex drive, thoughts of suicide and pessimism, said Dietz. He added that "plenty of successful people" have that mental disorder, with the result that they "never feel good about themselves."

From the age of 18, Hinckley had features of a narcissistic personality disorder, Dietz said, including preoccupation with fantasies of fame, manipulating personal relationships and a sense that he was entitled to things he had not earned.

The jury yesterday also heard testimony from a woman who worked at the Golden Hours Motel in Colorado where Hinckley stayed for 16 days just before the shooting.

"We all really liked him," Virginia (Ginger) Aucourt testified. Hinckley was an "exceptionally neat" and undemanding guest who enjoyed playing with young children and once took a look at the "Levi action" when a group of young girls crossed the motel parking lot. Hinckley smiled at the remark as Aucourt grew red-faced with embarrassment at what she had said.

"He was just a normal, you know, all-American-type boy to me," Aucourt told the jury.