The apparent positions of stars and constellations do shift over the course of a year due to the Earth's orbit around the Sun. However, the changes in their positions are relatively small and may not be immediately noticeable to the naked eye. This phenomenon is known as "annual parallax."
The reason we perceive the constellations and stars as relatively fixed throughout the year is because the distances to the stars are vast compared to the size of Earth's orbit. The stars are so far away that the change in our perspective from opposite sides of the orbit is negligible. Therefore, the constellations appear to remain largely unchanged.
However, if you observe the night sky carefully over the course of several months, you will notice some shifts in the positions of stars and constellations. The most noticeable changes occur with objects closer to us, such as the Moon, planets, and some nearby stars. These objects exhibit more apparent movement against the background stars due to their proximity to Earth.
Additionally, the position of the Sun in the sky throughout the year affects our ability to see certain constellations. The Sun's position determines which constellations are visible during different seasons. When the Sun is in a particular region of the sky, the corresponding constellations are hidden by its glare and not visible at night. As the Earth orbits the Sun, different constellations become visible in the nighttime sky.
In summary, while the constellations and stars do shift their positions slightly over the year due to Earth's orbit around the Sun, their vast distances make these changes relatively small and not easily noticeable to casual observers.