Weighted blankets?

I was browsing the internet for something that might help my 3 mo stay asleep because he has such awful startle reflex. I've tried the love to dream swaddler, halo swaddler etc. he still jumps with them. The only things that works is me putting my hand on him adding slight pressure or just holding him. I came across sensacalm weighted blankets that are supposed to help a child feel secure. Do u think this would be a SIDS risk? I'm not sure how heavy they are but I don't want to chance anything. Anyone ever heard of this?