2000 not shifting into drive. (Sometimes)

2000 V6 280k miles Auto ext. cab.
I had the transmission fluid changed on 08/22. (Toyota ATF)
I let my Tacoma warm up before I drive.
It sometimes does not want to engage into drive.
It happens when parked flat or on a small inclined.
It has happened four times this year.
Once I shift it back into park and back into drive, it's good.
It has happened right after driving, engine is still warm.
The fluid level is checked every three months.

Any suggestions?

 

Maybe the range selector is going bad. If you put a Tacoma transmission in drive electrically it must be told to put the solenoids in 1st gear, but mechanically in drive position it is default in third gear. Next time it acts up see if you can mash the gas to get it to move at all. If it moves ultra sluggish it is probably in third gear indicating you have a bad range selector.