It is believed that during its movement in the Galaxy the Solar System has repeatedly passed through dust clouds at intervals

It is believed that during its movement in the Galaxy the Solar System has repeatedly passed through dust clouds at intervals of 26 to 100 million years. Why does this phenomenon occur? Aren’t the clouds moving like the Sun around the center of the Galaxy?

Dust clouds can have different orbital parameters than the Sun. The intervals of the passage of the solar system through the dust clouds are less than the period of the Sun’s revolution around the center of the Galaxy (250 million years).