Randomly instant death when reopening a world

Twice this has happen to me when I reopen a world I instantly die at the world's respawn point even though I wasn't even at that location when I previously exited. When I click respawn, I come back at the world spawn point(because I use a portable bed I place & destroy to avoid nights) & collect all my stuff. This is very frustrating because not only I lost a majority of my levels, but I'm afraid I might lose a very powerful enchanted diamond pickaxe I created. Note: That this doesn't happen all the time, it happens very randomly.