When adding Rigidbody to my character, it flies upwards.

Hi guru.
I have already searched some solutions to solve a problem which characters are overlapped each other.
The solution I found was to add a rigidbody to each character.

However, after applying the rigidbody to my character, they starts to fly everywhere like a ball(?)…;ㅁ;

I gave ‘Mass 60’, checked ‘Use Gravity’ and Discrete for ‘Collision Detection’
I’m using a Capsule Collider for my character without any Material which means that it sets to None (Phsics Material).

Please give me some advice to fix this problem and thank you all in advance!!

Under Edit/Project Settings/Physics, make sure the Y component of gravity is negative, like -9.81