When I started playing Fallout New Vegas on my laptop after 2 to 3 hours playing with my character, his/hers head just exploded for no reason. That happens to all the characters I created so far. Since last Wednesday after trying to reach a area it started to happen more frequently. I saved the game every time I moved to see if I could get to where I was going until now that after the character dies I load the game and dies again.

I can only guess, because I can't play FNV 1.3 patched at all. Maybe your character is highly irradiated and that is what is killing them over time. Pop a RadAway or four of them asap. Or perhaps poisoned.