BodyPosition wont work what's wrong with my script how could I fix The Problem that im Having?

I don't know if its my script but Its not workign lol

local model = script.Parent
local start = model.Start
local platform = model.Part
local End = model.End
local Bposition = platform.BodyPosition

while true do
    Bposition.Position = start.Position
        wait(3)
    Bposition.Position = End.Position
        wait(3)
end