You don’t need to get the vehicle entity, you can simply use IsPedInAnyVehicle and in a while true use Citizen.Wait(0).

So this should work:

Citizen.CreateThread(function()
	while true do
        if IsPedInAnyVehicle(PlayerPedId(), false) then
             DisableControlAction( 1, 86, true )
        end
        Citizen.Wait(0)
    end
end)