Unit Circle

local part = script.Parent
local RunService = game:GetService("RunService")

local degree = 0
while RunService.Heartbeat:Wait() do
    degree += 1

    local x = 15 * math.cos(math.rad(degree))
    local y = 15 * math.sin(math.rad(degree)) + 20
    local z = 1 (or degree / 10 [if you want part moving])

    part.Position = Vector3.new(x,y,z)
end