It is recommended to take a shower just like you would at home. That is, leave the water running through the entire shower. The hot water system is designed to deliver a continuous, comfortable flow of hot water and that’s the way it works best.
Shutting off the shower with the showerhead button wastes water. Each time this is done, the showerhead “trickles”, filling the hot water line with cold water. This cold water has to be purged from the line each time the showerhead is turned back on. Tests have shown that this will not save water.