violent shaking

This has happened twice to me, but it is very disturbing. I've turned my key half-way and waited for the glow plug light to go off, but when I turn on the ignition, instead of starting like normal, my car shakes violently and makes a noise that makes me think that my engine is beating itself to death. Kind of a boom, boom, boom. As anyone with a brain would do, I abruptly kill the engine. When I try to start it again it acts like this never happened and runs like a dream. What the heck is going on here? My '02 Golf TDI has had it's issues in the past, but nothing scary like this. Does anyone have a clue what this could be?

That happened to me once, but I couldn't reproduce it. It might have been a stuck cutoff valve.

haven't found any more posts on this. i had this happen to me as well.

really freaked me out the first time, considering the motor only has 16k on it. it happened right after a random rev up. i was waiting on a red light and quickly got the RPM to hit 5000 in neutral. as soon as it came back down to idle it started shaking real bad, though the RPM kept right around 900. cycled the key and it was gone like a bad dream.

a few weeks later i deleted my snow screen(what a difference!) and shot the RPM's into the red section again. there it was again. it sounded like two of the four cylinders were misfiring. no codes were tripped, no smoke while it happened. and this time i shut off the ignition, started the car right back, and it didn't go away! this time i gave it a few taps on the accelerator and higher RPMs didn't even it out. it was still sputtering, choking, kinda having a seizure. shut it off again, started it and something got unstuck. it was fine again.

i do have a racepipe so it wasn't the cutoff. not that i really tried to reproduce it, but i've definitely hit higher RPMs again since, both in neutral and in gear. engine is doing great under all conditions. all the mods in my sig are still there. if anybody cares to help analyze this, please feel free.