1997 Toyota Camry Transmission not engaging into gear

This is a problem that occurs intermittently. The engine starts/runs and does not show an overheat condition, but transmission will be in "Nuetral" regardless what gear the shift lever is in. If car is shut off and restarted it "may" engage in R or D, but sometimes there is a wait involved or restart. Also, this happened several times about a year ago, before we stored the car for 9 months. We started using it again about 2 months ago and it was working fine for 450 miles until last night when it went into "Nuetral" (while in Drive) after 15 minutes of driving and a left turn. I shut the engine off for a few minutes then all worked fine for the 10 minute drive home. This morning it engaged into gear correctly only 3 out of 10 times, not counting "Park" which is the gear we'll leave it in for now.