If you are thinking about using this collar while sleeping, the first thing to know is that the product is designed to reduce the range of sudden bending, turning, and extension. When you lie down, especially on your side, your head can easily turn against the collar, which may cause pressure on the jaw or throat. The product information does not mention sleeping as an intended use, so it is safer to treat sleep as something to discuss with a doctor or physiotherapist. They can tell you whether a different type of support is more appropriate for overnight use.
Driving is another activity to approach carefully. A collar of this type restricts head rotation, so it becomes harder to check blind spots or look over your shoulder. If you wear it while driving, use additional mirrors where possible and keep your neck movements slow and intentional. Some people find it safer to wear the collar only outside the car and take it off before starting the engine. In the end, local laws and your own ability to control the vehicle safely matter more than comfort.
For side sleepers, a neck collar can dislodge during the night; it may also push the head into an awkward angle. If you do get permission to wear it to bed, place a small rolled towel or travel pillow around it to keep the collar aligned, and check your skin for pressure marks in the morning. If you wake with a stiff neck, a headache, or numbness, the collar was likely not suitable for overnight wear.
In short, use this collar for periods when you are awake and able to monitor your own comfort, unless a specialist specifically tells you to sleep with it.