This sign can be used to mean such things as enthusiasm, motivation, and/or caffeine. (No, I'm not making that "caffeine" bit up. The "Starbucks" crowd have to have ways of discussing their habits and it seems they get their daily motivation from a cup of coffee.)
Rub your hands together "enthusiastically."
ENTHUSIASM = "motivate"
Note:
Often the concept of "motivation" could best be signed by using the sign REASON, as in "What was your motivation for learning sign language?"
See: REASON
Notes: