Baby moves a lot when I try to sleep

Jam
Now, whenever I try to sleep and position myself on my left or right side, my baby always starts squirming and kicking strongly, and I often feel multiple limbs moving. I am 31 weeks pregnant.
Does this happen to anyone else? Do you know why it happens -- is it just baby repositioning herself after I position myself? I worry that I am hurting her when I put pressure on my belly, even from the sides.