I've done enough speaking now to realise the pre-talk jitters can be harnessed by a dribble two bounces as well. If I'm standing, I usually set 2 markers to make sure I stand in 1 spot, then do a quick scan of my cheat sheet, look at the number of people then set my timer and start. Interesting point about rubbing hands and clasping. This is a classic sign of discomfort and signals to the audience the speaker is nervous.