Yesterday I was playing on Experimental server "DayZ DE 0-2 (Experimental/Unstable)". I was heading from Nagornoe to Kamensk in a Sedan. I almost reached the military base between the two cities, when I suddenly died in the car.

There was no apparent cause. I didn't hear gunshots or my character screaming. Just the black screen "You are dead".

So I posted a video recording about the death on reddit, hoping maybe someone had an answer:
Link to post

(That map on screen appeared because I opened Steam Overlay just before I died)

So today I got a response saying they found my car a few hours later on the road with the engine running, and I was sitting in there normally, like I was alive, looking forward. They couldn't "kill" my character. Link to comment thread with explanation
This confirms that it was indeed a sudden death.

The game version was 136887 (I might be wrong, but it was the latest experimental patch where vehicles are currently enabled and are spawning in working condition).