What to say when someone is "activating" their super powers, without actually saying it?

I have a character with telekinesis and I'm trying to figure out how to say he is getting ready to fight without being super blatant about it. Blatantly saying they're turning on their powers just feels off.

If this helps: Usually when this character starts using his powers he will open his hands and there will be a low warbling/vibration frequency in the air. It also causes lights to flicker at times.