After dying I do not respawn at bed because it says it is obstructed

I set the spawn point on my bed. When I die and respawn it takes me back to the world spawn point which is very far away. It was happening on occasions, but now it happens every time I die. I then sleep in my bed and set the spawn point, but it makes no difference. I always go back to the world spawn. The bed is not obstructed or blocked. I have also tried different beds and it still happens.