2005 Nissan Altima lights flashing, car locking on its own

Hi lkp95,

Thank you for the donation.

Symptoms indicates the security system is being activated and the most common cause would be the door switches.
Check if any of the door switch covers are dislodged or damaged.
Check all doors for proper alignment.

Does the door ajar indcator lights sometimes tun on while driving?

The other possible cause would be a fault with the Body Control Module which would require appropriate diagnostic tools to check.