Nice car you have! Mine does the same also if I keep the water level between the min and max. Now I'm running it just below minimum and it's fine. It's a feature of the expansion tank cap to let pressure off too easily. During the summer I ran the car with the ignition relay removed and shorted with a jump wire. This way the cooling fan keeps cooling even after you switch the car off untill the temperature comes down.
My temperature issues are mostly turbo related and I didn't have these with the standard engine ever. So you might wan't to flush the radiator and change the thermostat just to be safe. If your having any temperature problems while driving or oyur fan kicks in too late, then I can warmly recommend the Toyota 82 degree thermostat. It opens slightly earlier than the original one and when it opens, it opens way more.
If you can you might want to try another expansion tank cap if you cap.