you gave aperfect description of ADult or Spasmodic Torticollis. Essentially the neck/head doesn't move for a while (like when sleeping) and some muscles go into an intence spasm.

Making it move gently can relieve(some people can be also be low in magnesium, sodium etc which can cause spasms). Heat and gentle forced but sustained movement seem to work best, as does adjusting your sleeping position. Stress, overworking the shoulders &/or neck or not moving during sleep {or all above} can easily lead to torticollis.

Mine was relieved greatly by buying new pillows and fixing my electrolyte levels (they were out of wack). Every time I slept on my new & expensive "memory foam" pillow I would wake up to intense pain and a stuck head. Turns out the new pillows made me sleep more still - and it made my tired old body move very little at night - thus the neck would go into spasm overnight.

Whatever your issue- it is no fun, to say the least! Good luck and relief soon!!