The "lifting his head up" thing was probably him periscoping. It is completely normal. It is what they do in the wild so they can see over the Savannah grass. Basically to scope out their environment for food.

The yawning is also completely normal. Usually they will yawn directly after a meal to realign their jaws, but occasionally they will yawn for no apparent reason. "yawning" is not aggressive. Hissing and striking is.

If you are this nervous around the snake, something is wrong. Next time you feel like you want to handle the snake, have someone who is not afraid close by in case you feel uncomfortable.

Please don't be afraid, these animals cannot hurt you.