taco neck
n.— «On a Tuesday afternoon in March, I woke up with what I call “taco neck.” The muscles on one side of my neck had locked, and my head leaned to the other side, as if I was about to take a bite from a taco.» —“Ending with a question” by George Rede The Oregonian (Portland) June 2, 2008. (source: Double-Tongued Dictionary)