Doors Lock By Themselves

OK, it's a 2002 Xterra SE 4x4. I had the battery out last week (working on radiator hoses) and now when I leave the car unlocked, it locks itself!

I tried locking/unlocking with key fob three times; multiple fob pushes; starting & shutting off. Takes more than a minute or two, but when I get up, it's locked.

I changed fob battery, still no love...

I can't find anything in the owners manual, anybody else run into this???

Thank You!

OK, another member pointed me to a page in the Owners Manual under "Pre Driving Checks And Adjustments" where it states -

Auto Relock
All doors will lock automatically within 5 minutes unless one of the following operations is performed:
* Any door is opened
*A key is inserted into the ignition switch and the key is turned from OFF to ON

I wasn't opening the door...

Thanks to all for your help!