I haven't seen this as a symptom anywhere, but just wondered if anyone else had had the same thing. I'm 13+4.
Right from the very early days (i.e. the 2ww...) when I wake up in the morning my entire body tenses from the shoulders down to my calves in a wave (best way I can think of describing it). Sometimes it goes down the sides of my torso, other times it goes across the bump. Not painful at all, just very strange. Actually happened the other day when I had just got out of bed and was standing, rather than lying down - so it's not like cramp at all.
I keep meaning to ask a midwife or something, but keep forgetting(!).