Depends on how hard you're trying to get out.
Seriously, I've been wrapped
inside a blanket (not tucked it but wrapped like a papoose) and if done right (such as having corners knotted together and having the blanket wrapped
tightly around a victim) can be a
bit restrictive. But by itself it's
not going to restrain anyone making any serious effort to get out unless they're really ill, weak, tired, drugged etc. or unless some extra element like ropes or straps are added.
Dare to be different... and make a difference.
To boldly go where no one in their right mind has gone before...