Chevy Lumina stopped running.

1997 Chevy Lumina stopped working. One day I drove to a shop and then made a stop at another store. Everything was fine.  When i turned my car on to go home, the engine failed to start up. i tried again and the engine started but the car was kind of shaking and i could smell really bad gas or oil scent. as i was driving home the car seemed to struggle when accelerating (i was able to go the 45 speed limit, however) and when i pulled to the stoplight it would shake even more than it did before. i made it home and luckily my girlfriend had another car i could use for work. when i tried starting my car a few days later, the engine started. i put the car into reverse but when i pushed the accelerator, the car would not move. it felt like it wanted to move but it was stuck or something (the car would push back and forth slightly but wouldnt actually move). even when applying more and more pressure to the accelerator, the engine would rev up louder but the car wouldnt move. the car has a history of the engine starting but then stopping. then it would start up on the second attempt and run fine. ive brought my car into a repair shop more than once for this but of course every time i brought the car in it wouldnt do this for the mechanic. it doesnt happen all the time either. also, my car had a history where in neutral or when in drive while holding brake the car would shake a little bit and the engine would whir funny for a moment but then seem to reorient itself.  this didnt happen all the time or even very often.  i don't know very much about cars so I have no idea what is wrong with it. any ideas on why this would happen? i havent brought the car to a mechanic after it stopped working as i am low on money at the moment and thought i would ask online first.