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
Graceful is a synonym for pretty. It begins with the letter g.
Some positive words that begin with the letter P:perfectphilanthropicpoisedpowerfulpragmaticpreciousprettyproductiveprofessional
Against, starting with, beginning at, taken away, originating at...
nice looking
Unique