Hello my question is Science says atoms of solids are in constant motion, then why solids don’t change their shapes continuously?

Good question.

The motion is primarily vibrational but also rotational. The scale of the vibration is not large enough to cause the material to flow.

(Yep. That's my answer and I'm stickin' to it).

In fact, you can have solids changing shape, but with an application of force. An elastic band is a solid, but it can change it's shape, like plastic bottles. However, that has more to do with physics.