I am typically a side sleeper and I wake in the middle of the night or in the morning with a very stiff neck...
If you don't do this already, try disconnecting from technology at least 2 hours before your bedtime. No computers, no smartphones, no TV. Also don't read newspapers or anything that might be upsetting/get your mind going during that time. Read a book (the old fashioned kind made of paper!), go for a walk or talk with someone about casual topics (talking on the phone's OK, just no texting). Could any of this help?