Liz I would not have made the connection if you hadn't have suggested it -- but a pillow helped here, too.
DS is extremely active in his sleep - we hear him banging his head, rolling over and hitting the side of the cot and then I can tell he sits up, gets himself turned around and then thuds back down again. I go in to turn the heat down when I go to bed and he's all over the place.
I started with a pillow about 2-3 weeks ago. He's had a small toddler pillow since 12 months old, but it was more for play....he liked to put it on his lap while playing in the living room, and things like that. Couple of weeks ago when he was sick I put it in as a way to keep his head elevated while he was sleeping and have kept it in there. Every night that I've gone in to check on him, he's sleeping in more or less the same place as I put him in when he went to bed...although sometimes he does turn himself around length-ways and sleeps on his pillow instead of just his head.
To make sure he didn't decide it was a toy, and to stop him from putting it over his face at night, I put it underneath the sheet, so he can't move it. The one night I forgot to put the pillow in when I was making his bed, I snuck it in when I went to bed, and sure enough he woke at 6am giggling and laughing because his pillow was in there
But definitely have had more calm sleeps since I have put that pillow in there!