My car starts "weakly." It is difficult to describe, but the symptoms seem fairly consistent. When I turn the key/start the car, I can hear the motor turning over quickly and very well. But it takes a second or two for the vehicle to catch on and start. I get the impression it's having a hard time getting something - fuel or air, perhaps.
When it does "catch on" and start, it is a very quiet, low key idle - consistent, but low powered. I noticed because my family's red 2000 Grand Prix GT (non-super charged, 3800 engine) starts very powerfully, and catches on a little bit quicker then mine. It's idle is louder/more powerful as well.
Here's something else that might help. The symptom described above occurs if I'd driven the vehicle less than a day or two before. If I don't start it for several days, it will not start at all. What happens then is the following: I turn the key, the motor turns over quickly and great like normal, but the car doesn't "catch on"/start at all. I have to give the car some gas with the accelerator to get it started. Then it starts normally and idles great (but still relatively low-key compared to my family's GT).