if I were you I would start by checking out as many videos of robots as you can.
Decide on a design that you like and that you think you would have a chance of being able to build and go from there.
You say that you're an electronic engineer?
So you're happy enough with the electronics side of things? Microcontroller, circuit design and power supplies etc?
You should look at arduino for easy to use and programmer controllers.
Decide on a design. Look at what materials you could make it out of and then try to put it all together.