If you are interested in delving deeper into the performance practice of baroque music, a good place to start is with Judy Tarling's book: Baroque String Playing for ingenious learners, 2000, Corda Music Publications. Judy's book summarises relevant information from many baroque treatises on string playing and performance style and is an excellent resource for today's players of baroque music.
If you are keen to go back to the origianal sources, here are a few to explore:
Leopold Mozart, Versuch einer gründlichen Violinschule, Augsburg, 1756 (translated into English as A Treatise on the Fundamentals of Violin Playing by Editha Knocker, OUP)
Giuseppe Tartini, Traité des Agréments de la Musique, translated into French by P. Dennis, 1771 (English translation edited by E. R. Jacobi, Celle and New York, 1961)
Johann Joachim Quantz, Versuch einer Anweisung die Flöte traversiere zu spielen, Belin, 1952 (translated into English as On Playing the Flute by E. R. Reilly, London and New York, 1966)
If you are performing unaccompanied Bach, you may find the following book helpful:
Joel Lester, Bach's works for solo violin: style, structure, performance, Oxford University Press, 2003
International Music Score Library Project (IMSLP)
Many manuscript and first edition prints of baroque music, including various editions of all the pieces explored in thier resource, are available online from this website.