when you die you don't go back to the same spot where you spawned, You spawn in a random spot in the general area.

To replicate:
start new game
remember where you spawned (exact co-ord)
die / kill yourself
when you get respawned your not at the original spawn, you are somewhere nearby. but not the same point. (i've been up to 16 cells away in x and y)
repeat kill yourself.
and you'll spawn somewhere else again in around the same area
so its costantly changing where your apearing

it doesn't appear to happen when you set a bed and sleep in it.
(while your bed is still in place you spawn at your bed)
remove your bed and it goes back to again not static spawn point