It means you startled your snake. How fast did you reach into the cage and at what angle? Did you give your snake time to "smell" your presence in the tank or did you just reach in and grab him? Its best to just reach in slowly and let your snake get a whiff of you and then try to pick it up from the middle of its body. Try also approaching it from a more sideways approach, its lets threatening for the snake. I know thats not easy if you have a regular aquarium tank that opens on the top, but after a few tries you'll get the hang of a better sideways approach. And after a while of handling your snake, it will also get used to your scent and know that you mean it no harm. good luck and if you can post some pics of your snake. We'd all love to see it.