Inspiration can strike at any moment, and be gone just like that. Where does inspiration come from astrologically? You have a few places you can look at: the 5th house, Neptune & the 12th house, and the asteroid Muses.
The 5th house is the house of creativity, and the first place you look to for inspiration. The sign on the cusp and planets in the house can show what inspires you and how you’re inspired, if it comes easily to you (the Sun, Mercury, Venus, or Jupiter in the 5th house) or if it’s something you struggle with at times (Saturn, Uranus, or Pluto in the 5th house). When you have positive aspects (sextiles and trines) by the transit (moving) planets to the 5th house cusp or planetary ruler, these can be times when inspiration is easy for you to find, and your creative energy can flow. Hard aspects (squares and oppositions) can make inspiration difficult to find, it can come and go, or you feel blocked. A conjunction to the cusp or ruler can bring heightened energy one way or the other, depending on the planet involved and other aspects occurring at the same time. When a planet transits the 5th house, this can bring inspiration and your creative energy out more, or block it more. Jupiter, Mars, or Venus in the 5th house can bring you the most inspiration, while Uranus in the 5th house can bring erratic streaks, and Saturn can bring the biggest blocks.
Neptune and the 12th house rule our imagination and soul, so when either of these are being activated with transit aspects, you can experience a surge in energy for your imagination, and a stirring in your soul that inspires you. Again, the positive aspects make it easy, while the hard aspects make it difficult, and conjunctions can amplify either way. Transit planets in the 12th house can make your imaginative energy stronger and easier (Jupiter, Mars, Venus), or harder to manage well (Saturn, Pluto, Uranus). The sign and house placement of your Neptune, and the sign on the cusp and planets in the house of your 12th house can show what inspires your soul and how your imaginative energy is expressed.
The Muses are a group of asteroids that are linked to inspiration - of course! These nine asteroids can give us more creative energy in the natal chart, and when triggered by transit planets or the transit Muses are aspecting our charts, we can be much more inspired. You can find the location of your Muses and get an ephemeris for them on astro.com. The asteroid Muses are:
22 - Calliope: Muse of Epic Poetry
84 - Clio: Muse of History
27 - Euterpe: Muse of Music, Song, and Elegiac Poetry
62 - Erato: Muse of Lyric Poetry
18 - Melpomene: Muse of Tragedy
33 - Polyhymnia: Muse of Hymns
81 - Terpsichore: Muse of Dance
23 - Thalia: Muse of Comedy
30 - Urania: Muse of Astronomy (and astrology!)
Mercury Retrograde in Sagittarius: December 2017
January 2018 New & Full Moons
December 2017 New & Full Moons
Jupiter in Scorpio: October 2017 - November 2018
Saturn in Capricorn: December 2017 - March 2020, July - December 2020
Saturn in Sagittarius: December 2014 - June 2015, September 2015 - December 2017
Saturn in Sagittarius for Each Sign