hi, 

i have a 2000 chevy cavalier, 4 door, 34,000 miles.

just bought the vehicle from private dealer.

and is my second vehicle ever.

my issue im having is that the car has a tough time starting, some days it starts right up, but often times when it does start it will begin to stall, the rpm fluctuates from really low and sometimes seems like the car wants to drive itself without me pushing on to the accelerator.  also feels like the car loses power when driving. today is shut down on me, like it was really tired and needed to sleep. there is no funny smell, nor is there and black smoke coming out of exhaust, and the dash doesnt indicate any warning lights. when i stop for a red light or a stop sign i fear the car when it behaves as though it wants to shut down i actually put it in park and rev the engine slightly so that it wont die, but even then i think it majes it worse?

i bought a new battery because it needed it. also oil is ok, and the rest of the fluids is ok to, and also just bought a new tire.

there is no fluid leaks, no knocking noise, its in great condition, no rust, but its getting worse and im not sure what the problem is, need help diagnose issue and could use some expert opinions as i am not an expert whatsoever. hope that helps, thank you so much.

today i asked a maintenance man at a oil changing station if he could offer advice, he came to my vehicle i explained to him this, and he tried to start it, he had to hold the key to ignition until it started, said it could be spark plugs, fuel pump, or catylac converter.