1999 toyota avalon, starter location, or engine view diagram

It's under the battery. see instructions below for removing.

REMOVAL & INSTALLATION

1. Disconnect the cable from the negative terminal of the battery.

1. On some early models with cruise control, you may have to remove the battery.
   
   Also on some models with cruise control, remove the actuator cover and disconnect the wiring harness. Remove the three bolts and then lift out the cruise control actuator. Remove the bracket from beneath the actuator and put aside.

1. Peel the rubber boot away and remove the nut and disconnect the negative battery cable from the magnetic switch terminal on the starter. Disconnect the electrical connector also located on the magnetic switch.

1. Support the starter by hand and remove the two mounting bolts.

1. Remove the starter from the transaxle.