How to move object at random direction,that changes after some amount of time?

Hello there, and welcome to Unity Answers!

Here are some links to get you started on your journey:

• Random behaviors can be obtained with the "Random" class: http://docs.unity3d.com/Documentation/ScriptReference/Random.html . You will also need to "seed" the class; a typical way to seed a random class is to use the current time; System.DateTime can be used for this.

• One way to move an object is to modify the object's "Transform": http://docs.unity3d.com/Documentation/ScriptReference/Transform.html

• Finally, ray casting can be accomplished with Physics.Raycast: http://docs.unity3d.com/Documentation/ScriptReference/Physics.Raycast.html

Good luck, and feel free to create a new question (ideally with some of your code) if you get stuck.