I wonder if it is a security thing. Try and find a nice cuddly toy for him ( but light weight ) , tuck the blanket under his arm ( as that where it should be ) and see if he will hold the toy . This will still make it nice and warm cosy area .

yeap we have one who at 9 still sleeps with something on his head, thin muslin works well or the old school cotton nappies

We would use a very thing muslin. Wrap so he could breathe through it as nothing we did stopped him he would even try pull his sheet off to pop around him.

Use to make me pa if walking in and seeing thick blankets on his face

Yes I reckon those The cotton weave blankets are good – warm and have holes for breathing too!

Is it possible he thinks his head is cold or you have an airconditioning vent that is blowing air onto him??

What a worrying situation! I think I agree with the crochet blankets

Get the crochet blankets (with holes).
He might not like it, but his safety comes first!
My son wears x2 sleeping bags and has x3 crochet blankets (it gets incredibly cold here at night) . he wraps himself to a worrying point, but since using crochet blankets, I can sleep in peace at night

that is scary, what if you wrap him in a one piece jumpsuit .

I use a crochet blanket or a waffle blanket both breathable. Mine is in a sleeping bag but she likes the extra warmth and so we use those so I’m not freaking out at night. Good luck

Can you tuck the blanket under the mattress? We used to throw the blanket in the baby to make sure she would pull it off her face, then we’d say peek a boo and she thought this was funny. The cotton weave blankets are good – warm and have holes for breathing

If a sleeping bag is not working as he prefers the blanket on his head, try an open weave blanket, a perfect example would be a crochet blanket, thick and warm, however has holes so the baby can breathe.

Hey, he has a mixture of blankets but prefers the thick soft ones. So that’s the main concern if it was his really thin ones I wouldn’t have an issue.. Suggestions on what to look for in a sleeping bag?

I’d definitely go back to a sleeping bag. Just for safety! What type of blanket does he have? My sons blankie is a very thin muslin cloth which, even if he covered his face, he’ll be able to breathe through.,

try putting him back in his sleeping bag and get him a blankie with a toy on it. i got mine from best and less and it might comfort him and give him something to hold onto without comprimising his safety. They are only small but big enough for a baby