An intermitten problem.
When first starting the 2001 toyota tacoma, automatic trans. V6 truck it acts as if the gears will not engage. When giving it extra gas it moves slowly, the after a few seconds of this the gears shift and it drives normally.

If you haven't been changing the transmission fluid and filter every 30,000 miles the clutch packs may be shot. You may want to drop the pan and check things out.

Look at the backing plates of the rear brakes. See if you see them wet from leaking axle grease.
Better still, pull the rear brake drums and look for contaminated rear shoes.
A leaking axle seal onto the brake linings will act like glue and hold the rear wheels until it warms up a bit.
Definitely check that trans fluid also.