Thank you for your question. Pins and needles are most caused by nerve conditions. Because this only occurs when you lie down, it has to mean that the change in posture is irritating your nervous system, most frequently the nerve roots from your spine. There is also a nervous condition called restless legs syndrome, which tends to occur at night when lying down. Treatment consists of taking a nerve stabilizing drug, an example of one would be Lyrica. Please consult a doctor, as poor sleep can be very detrimental to your general health. Do not hesitate to ask for any further information .