leading time traveler causes of death (respin of last week's last xkcd) [content lost and/or corrupt during attempt to access email]
[past] a malicious AI causes your time machine to land you precisely over a previous instance of your body producing causality feedback resonance and an explosion of your timeline [past] preventing your own access to a time machine via the butterfly effect from breathing [next year] time war [two years in future] metatime war [future] being the only person with only one head during a mass purging of apelikes akin to our own evolutionary history [either] forgetting to take your return device [either] having your return device stolen by a supervillain who followed after you [either] having a malicious AI virus that had infested your time machine assassinate you now that a covert protective AI can no longer monitor you [near past] being taken over by a dissociative persecutory alter and, during a dissociative fugue, forcibly convincing your past self to never travel back in the first place [near past] kidnapping your past self and torturing it out of fury [near future] switching into a frightening alter that you're dissociating from existing, scaring your future self, and stimulating your future self to go back in time to stop you [either] stimulating a global time war in conflict with yourself whilst trying to realise you have DID [past] sharing your time device with an urgent powerhungry individual [future] sharing your time device with a consortium purpose-built to prevent them
finally,
[either] being so scared of time wars that you hide out in the distant future or distant past, possibly on another planet, for so long that you die of normal causes
[DID] "when i got in my time machine, i blanked out. some time must have passed. when i woke up i was surrounded by copies of myself, all looking at me meaningfully and knowingly and telling me that i knew what I had to do, and I had better go do it. but i don't know what they're talking about. is it obvious somehow?"