Moving a car then teleporting it back its original position not working?

The problem is that you're trying to set the CFrame of the model to a Vector3. This doesn't work since CFrames have additional properties besides a Vector3 position.

However, you can create a CFrame from a Vector3 using CFrame.new. NOTE: by default, this will set the CFrame's orientation to 0,0,0.

local model = game.Workspace.Car
local originallocation = model.PrimaryPart.CFrame

while true do
    for i = 0,100,0.1 do
        model:SetPrimaryPartCFrame(CFrame.new(model.PrimaryPart.Position + Vector3.new(1,0,0)))  
        wait()
    end
    model:SetPrimaryPartCFrame(originallocation)
end

Changing the rotation is quite simple. The CFrame.Angles function will modify the orientation of any other CFrame, by simply multiplying both of them together.

CFrame.new(0,0,0) * CFrame.Angles(0,90,0)

But keep in mind that this function expects the inputs to be in radians, not in degrees. So the rotation might seem a bit, off. But fortunately there's a function that converts degrees into radians, as well as a function which does the opposite. It's math.rad and math.deg.

math.rad expects an input in degrees and converts it into an output in radians, which is exactly what we want.

CFrame.new(0,0,0) * CFrame.Angles(math.rad(0),math.rad(90),math.rad(0)) -- Rotation should be "Fixed" now!

Here's your script but with the changes:

local model = game.Workspace.Car
local originallocation = model.PrimaryPart.CFrame

while true do
    for i = 0,100,0.1 do
        model:SetPrimaryPartCFrame(CFrame.new(model.PrimaryPart.Position + Vector3.new(1,0,0)) * CFrame.Angles(math.rad(0),math.rad(90),math.rad(0)) )  
        wait()
    end
    model:SetPrimaryPartCFrame(originallocation)
end

You'll have to play around with the values to find the correct orientation.