This is a bug that occured several times to mates of me and to myself. If a mate (or I) was hiding in a bush (for e.g. as a sniper) and the server restarted (when you have been long enough in the bush) and you log in to any server you are spawned in the air over the bush and then die because of falling damage.

Probably the server tries to not spawn you inside an object and so it spawns you over the bush, but because the bush is not an ôbject that you can't stand on you fall down.

So if you respawn it will say "You are dead" and sometimes you will even see the messages of your bones that are breaking.
I am absolutley sure that you die because of falling damage. Each time it happened the body was lootable and only the pants were ruined. One time a mate stood right next to me when I spawned (and died because of this) and there was no zombie that could have killed me.

It would be nice if this bug was fixed. Otherwise bushes are a deathtrap for people who think it is a good place to log out hided in a bush.

PS:
I haven't tried to reproduce it yet (I don't want to die ;) ) and I think it won't work every time (since I didn't always die near bushes), but I am sure it does work if you try it several times.

PPS:
It is really important to stand completly inside the bush. (Only your gun may still be pointing out.) It works with big bushes (as tall as a player when standing) as well as with small bushes (bushes as small as a crouched player) (for e.g. the bushes that are all around at the Balota Airfield).