You've walked in on Mommy, and she's... relaxing. This is what she tells you, anyway. You don't actually know what it is - she's naked and touching her body! It's randomly appealing to you and your body responds accordingly.
Mommy assures you that this is the best way to relax, and that if you're having trouble sl33ping - which she concludes from you standing before her late at night - you should try it yourself. She gives you information on what to do and then goes right along with it herself