KansasRX300Guy

Hi all, I'm new to this forum and I'm kicking myself for not trying to find a community like this earlier. I have a 2000 RX300 with a weird shifting problem. If I take off VERY smoothly, everything shifts fine, up to high gear (4th?). Once I stop though, the car won't shift into the highest gear at highway speeds. However, I discovered that if I pull over, shut the car off completely for a few seconds (doesn't take long!) and restart, as long as I take off nice and smooth again, everything is fine, until I stop again. I think it's a computer issue, but I'm not a technician. Anyone else have this problem? If it's something a home wrencher can do I'm not afraid of saving a lot of money doing it myself. If it's a trans or computer problem though, well, we are well and truely screwed. Thanks!