How to make motor6d face a part?

I have an npc and i want his head to always face me, the player character. i tried using the simple CFrame.new(pos, lookat) for the neck motor6d but it doesnt work, it does strange things like make the head move a lot at one angle, and at another angle it moves slowly when i walk, and also sometimes it faces me, and sometimes it doesnt, i looks to the side, please help me.