Weird sound under access cab after/when reversing

Hello everyone. First post aside from my welcome post.

So. Just got an 06 access prerunner when i back up after parking for a bit i hear this brief whir, almost like something powering up and pressurizing or a phone on vibrate.

If I just stop anywhere and reverse and then drive I do not hear it. It is only on start up.

Edit: actually just heard it without needing to reverse, but again on start up.

Normal?

Aside from that I have slight shimmy at 1-5mph, but truck runs great!

 

Fluids checked? 100,000 miles servicing done?

 

Just got it from Toyota dealer and they said they checked everything. Truck only has 60k.

 

Probably abs self test. My 2010 does it

 

Cool. Thanks. Found one other thread mentioning it with a few people saying the same thing.