My travel companion...
When I drove my vehicle(a 4 door sedan), I kept my firearm in a unlocked plastic/pad gun case in the front passenger seat. I used a Plano or Docsil brand.
If I went out for a bit(restaurant, film, cigar, etc) I locked up the case and put it in the back rear passenger floor area or the vehicle trunk.
This was to avoid anyone having a clear view of a firearm case & to prevent direct sunlight.
If I would be gone for extended periods or going home, I'd remove the loaded firearm/case entirely.
I'm not in the "I leave my loaded guns lying around in the truck." crowd.