When I sleep on my side I have to make sure there is not too much contact or pressure at the neck or it will get compressed. Also, I sometimes flex the muscle on the opposite side and have to consciously let it go.

Also, this self massage helps me:
http://www.youtube.com/watch?v=duSNnBnqFts

I like it better than using a heat wrap. The massage increases circulation from the inside. The heat wrap is nice at first, but then when I take it off, my neck feels cold.

HTH some.