When I make unanchored parts, they glitch?

I'm sorry if this is nothing related to what this website is about, but I can't find anything about this anywhere. I don't know what caused it and how to fix it.

When I make a part unanchored, the part glitches. Like when I move away from it, it just stops falling and is in the air, but when I come close to it, it continues falling? Can anyone help me please?