The best way to sleep in order to fully relax the spine and improve circulation:
- Enough pillow (via thickness or number of pillows) to raise the neck just so that it is inline with the neck (i.e. the neck should not be arched up or down, but should be level).
- Lying on the side (left or right is your choice).
- Knees bent, as if sitting in a chair.
- A pillow placed between the knees.
- A pillow, partner, or large stuffed animal, placed between the arms.
Note: the knee and arm pillows are meant to keep the body aligned despite resting on one side, so that one arm or knee isn't hanging for extended periods of time, draining blood and possibly experiencing numbness.
Now, while the position described above sounds extreme, it is quite comfortable! This is how I sleep every night so long that I have enough pillows. If you aren't ready to adopt the entire position, simply changing one component of your already existing sleep position to one listed above will be helpful to your spine and circulation.