• Charles IV, Autobiography of Emperor Charles IV and Legend of St. Wenceslas, ed. & trans. Balaxd Nagy & Frank Shaer, Budapest: CEU Pr., 2001: is probably the closest one OP is looking for, but this bilingual edition (Latin original and English translation) is not easy to find and very expensive. The content itself is fortunately not so dry, I suppose, but it covered only up to ca. 1350, early years of his reign. Older (19th century) German translation, L. Oelsner (übers.), Kaiser Karls IV. Jugendleben von ihm selbst erzählt, 2. Aufl., Leipzig, 1899 is also freely available online, as long as you don't mind the old-style fraktur fonts. It is also one of very few autobiography written by the ruler himself in medieval Western/ Central Europe.

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• [NB: They don't focus on particular nobles.] Thietmar of Merseburg, Ottonian Germany: The Chronicon of Thietmar of Merseburg, trans. David Warner, Manchester: Manchester UP, 2001 is a readable English translation of the Ottonian chronicle. I also suppose that it is more readable than the English translation of the most famous Salian Chronicle, Ian S. Robinson (trans.), The Annals of Lampert of Hersfeld, Manchester: Manchester UP, 2015.
• Loyn, Jonathan R. (trans.), Noble Society: Five Lives from Twelfth-Century Germany, Manchester: Manchester UP, 2017: is a rare translated collection of medieval biographical works of non-royal aristocrats in the 12th century Germany.
• Otto of Freising/ Rahewin, The Deeds of Frederick Barbarossa, trans. Charles C. Mierow. New York: Columbia UP, 2004 (1953): is the standard primary text on the early years (1150s and 1160s) of the reign of Frederick Barbarossa (r. 1152-90), firstly written by his uncle, Otto of Freising.
• [Added]: If you are also interested in the life of medieval noble women, the life (as a saint) of St. Elizabeth of Hungary (d. 1231) is translated from Latin either in English or in German, though the former is expensive and the latter might be a bit difficult to find: The Life and Afterlife of St. Elizabeth of Hungary: Testimony from her Canonization Hearings, ed. & trans. Kenneth B. Wolf, Oxford: OUP, 2011.

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• Johann Schiltberger, Bondage and Travels of Johann Schiltberger: A Native of Bavaria, in Europe, Asia, and Africa, 1396–1427, trans. J. Buchanan Telfer, London, 1879 (Link to the scanned old English translation in Project Guthenberg): is a modern (though dated) English translation of Reisebuch. You'll have to take his narrative with grain of salt, however, and the scope of the work is largely out of Central Europe. There might be better old but modern German translations from the 19th century, though again with fraktur fonts. I also forgot to mention that he was the nearest contemporary figure as the protagonist of Game Kingdom Come: Deliverance.
• The modern German text of the autobiography of a very famous German robber knight in the end of the Middle Ages, Götz von Berlichingen (d. 1562) is also available on wikisource, apparently taken from the critical edition edited by Helgard Ulmschneider as Mein Fehd und Handlungen, Sigmaringen: Jan Thorbecke, 1981. Goethe adapted his life into the drama, and it is certainly interesting to read. [Added]: English translation of Götz's memoir is now found in: https://ghdi.ghi-dc.org/sub_document.cfm?document_id=3706