Cause of this noise from hot water baseboard?

Hi all, is the noise in this video caused by the pipe expanding and touching something like the wall or floor? I can't find where it's making contact with anything, could it be something else?

https://photos.app.goo.gl/xZhVR1ayFik88ELP9

Thanks in advance!

source https://hvac-talk.com/vbb/showthread.php?2226839-Cause-of-this-noise-from-hot-water-baseboard&goto=newpost