I'm no gear head and correct me if i'm wrong, but my moms car does the same thing. She was told it was a bad crankshaft position sensor. I don't think it'* completely bad, i don't know what the crap is wrong with it... just want the mechanic told us. The car only runs bad for about 30secs after you start it up. It'll idel bad, then sometimes die for about the first 30 secs. I was told once the engine gets in sequence it will run fine.
Like i said.. i'm no gearhead, just reminds me of a problem my mom had.
She drives a 91 or 92 bonnie by the way. I don't remeber which.
1995 SSEi 140,000 (mom'* now)
05 Altima SE 5 speed.