I've got a 1992 Z-28, factory automatic transmission, with a shifting problem. The car has approx. 91,000 miles on it....rarely drive it. About 10 years ago, I had the transmission fluid, filter, etc. changed. I've driven it about 10,000 miles since then. Recently, when starting out, the car bogs down when it normally would shift into second gear. RPMs do not go high...stays about the normal area. After a couple of minutes, it's fine...shifts perfectly. I thought it might be the trans. fluid, so I had it flushed...didn't change the filter. Still have the same problem. The only other thing that has been done in recent years is that the transmission speed sensor was replaced about 18 months ago.