Hi trecept,

Potential Solution

You could use :Lerp(), which needs the start and end points to animate a part smoothly from one location/rotation to another.

Solution

You could also make two parts, one is the invisible base, which is the root of the whole thing. Then, the other part is just what the people will see. Make sure to make the root invisible if you don't want it seen.

This is the same theory that our characters are based on. In our characters, there's a humanoid root part, which is invisible. Then, there are the rest of the parts which are attached to the HumanoidRootPart with a Motor6D.

At the end, make a model, put a humanoid in it, put the part you want to animate in it, put the base of the whole model, which should be at the center of the model(You could just duplicate the part that you are animating) Then, make the base invisible, since you only want them to see the one part that you're animating. The end product should look like this.

Conclusion

After you've followed the above solution(s). You can just click on the part like you were animating a character, and then just animate it. I think that animating NPCs is a bit different though, so make sure you pay mind to that.

Resources

You can find more information on lerp here.

You can find more information on NPC animations here.

Well, I hope I helped and have a nice day/night.

Thanks,

Best regards,

~~ KingLoneCat