My diesel engine won't start!

Hello folks,

I have a 2003 VW Jetta 1.81L diesel automatic wagon. Usually it starts just fine although it doesn't start instantly. But yesterday it stopped working very dramatically.

What happened was I got into the car and started it up as usual, no problems, then I drove it literally 30 feet away over to the hose to clean off the dozen splatters of bird crap that I have to clean off literally every day. I turned off the engine, hosed and scrubbed the car down and got in, and tried to start it up.

This is where it made the most awful noise. The best way I could describe it was like a smoker's cough -- it seemed to start momentarily but it was rumbling and staggering all over itself idling totally out of sync. It felt like it was lurching like a drunk man. (there was also an impressive cloud of white exhaust out of the back, although I'm not sure how much was steam) Then it quit. So I tried again, and each time, it seems to have power enough to turn over, it goes "GRUMBLErrrrrrGRUMBLErrrREGRUMBLErrrrrr.." like something is firing up but it's just not catching on. It really seemed to be wanting to go so I tried it a few more times but no luck. Even pumping the pedal didn't motivate it to go.

I don't think it's a dead battery, since I've had those before and that feels a lot wimpier and less lively than this does. I'm also not sure why it started just fine once then only a few minutes later decided to kick the bucket when I tried again.

There's half a tank of fuel still left and it had an oil change in November. The coolant is full.

Do you guys know what might be wrong with it? None of the auto shops in town are open right now so I'm looking towards other sources in the hope that more info will calm my panicking fear that something huge and expensive is going wrong or that its somehow irreparably died (like my last one did when the timing belt snapped)

Please keep in mind that cars and engines and everything like this is totally foreign to me, I'm not afraid to admit that all I know about cars is they're things that go forward when you push the button on the floor ??? so please explain your answers like I'm fully mentally deficient lol.

Any help you can give would really mean the world, I've been up all night with anxiety. 

Also willing to provide any additional info. Thanks!