Every morning i wake up with a stiff neck and have no arthritis or similar diseases. my pillows are confortable and have no ac. what are some causes?

Various: You may be slightly dehydrated. If not drinking 64 oz of water a day, increase consumption. Position can affect you as well. While your pillows may be comfortable they may still not have your neck aligned properly. If you are also misaligned verterbrae then you may also have stiffness in the neck in the am. Consider a chiropractor as well. Neck alignment can produce amazing improvements.

As we enter middle : Age, there is some degeneration of the structures of the cervical spine which may not be apparent on x-rays but do develop and can lead to this stiffness feeling. You can try some simple range of motion exercises and isometric stengthening ones and sleep with only one thin pillow. If it is still annoying, then try otc meds before going to sleep if no medical contraindications