Attractive, appealing, alluring, arresting (as in arresting everyone else's attention), and aesthetic (aesthetic legs, not an aesthetic person).
Words that mean the same as the word 'beginning' are: start, origin, outset, onset, inception, source...
Words beginning with you are limited to forms of you, youth and young. If you mean "Happy words beginning with a U sound," perhaps you refer to euphoric.
From the beginning.
start from the beginning
positive words beggining with n
roommate
Plentiful, populous, prevalent
Some positive words that begin with the letter P:perfectphilanthropicpoisedpowerfulpragmaticpreciousprettyproductiveprofessional
Graceful is a synonym for pretty. It begins with the letter g.
Some words that mean "from" include: originated, derived, emanated, and sourced.
Unique
nice looking