Hi, I having just googled these same sensations to see what they were all about and found your thread, hope you dont mind me posting!
I'm 32 years old now but I also first got the very same sensations when I was younger (about 13 years old) and was ill and had a fever. I vividly remember them to this day and can recreate the same sensations, even if i'm just sitting here doing something else. I dont meditate as a regular thing daily but I do occassionally.
The feeling is as though my limbs are very heavy like a dead weight, its almost as if I go into myself and even though i'm not moving the sensation all over is as though everything is very hard and sharp, weird to describe really!
I feel as though if I carry on i'm going to go into another world ha! Strange
x