IF, you have not tried it, don't worry, be patient, eventually
we all get to lay down in one and go up in flames at the Mandai
Crematorium.
In theory, a coffin is definitely claustrophobic. So logically if
you chance to lay down in one while you're still alive, don't
expect any comfort. It may be well padded (those high end models),
but still, you're in a box - how comfy could that be??