Is it possible to summon a random car with a name or a Tag?
These are the commands I've tested:
/summon car:car ~ ~ ~ {CustomName:"car"}
/summon car:car ~ ~ ~ {Tags: ["car"]}
This spawns a car. But the car is invisible and when you destroy it, it doesn't drop anything.
This also happens with "Team" and "Score".

You can't summon cars with names. You also can't summon cars with NBT data if you don't supply any car parts in the NBT.
Just /summon car without NBT spawns a random car.

Look at the NBT data of an existing car.

Ok how can you supply car parts?

How exactly can I look at NBT Data from an entity?
Sry if it's a stupid question...

/data get entity @e[type=car:car,limit=1,sort=nearest] gives you the data of the closest car

Thx I'll try it