Guided weapons? Sometimes the game does odd things, but it's not that strange to be one shotted out of the gate against a well equipped, experienced  player, or a bot on speed.

15 seconds is quite a lot.. with killshot i could probably make it to the last control point in 15 seconds.. so without any screenshots who knows what happened to you.. the best guess would be either mortars or guided weapons + your internet connection lagged (or server lagged), it tends to lag with me when I'm about to kill some enemy, and in result the lag unfreezes and i shoot in some other direction and die..

the other guess is your connection lagged, you were taken over by AI.. and then game ended lol, but it shouldnt end in 15 seconds.. so it must be first version of above.

There  was a bug a while back where you could spawn and instantly die. It was nothing like you described. 

I've had this same experience, where I just spawned and died right away. I couldn't figure it out, but it turned out just to be a very talented sniper, just waiting for me to emerge onto the battlefield. It's a pain and gets frustrating, but... it's part of the game. Gotta be a sniper, or a teleporting mech with a couple high level shotguns?