altima 01 starting problem

I have a 01 Altima GXE with about 35,000 miles on it. The problem occurs very infrequently. It is most common when I start the car. The engine and all the electronics come online but as soon as it turns on, it shuts itself off and it takes me a few times to get the car moving again. When I do get it moving again and when I am sitting at idle the RPM's will begin to flux and it sounds almost as if it was to turn off again.
I had the battery and alternator checked, both tested ok, so I am thinking it is a fuel issue, any ideas? Please help as soon as possible, thanks

try your o2 sensor it did it on my 90 240sx, once i changed it no more problem