Salamun Alaikum (Peace be upon you)
There are many prohibitions that Muslims have imposed on themselves which find no warrant from the Quran. Prohibitions covering certain garments, foods, objects, relationships, social interactions and much more covering a wide spectrum of Muslim thought are sourced from Islamic secondary sources. In contrast, the Quran provides very subtle guidance and attempts not to impose any difficulty on its worshippers.
"And strive in His cause as ye ought to strive. He has chosen you, and has imposed no difficulties on you in religion..."
What are our prohibitions in a nutshell?
The subtlety of the following beautiful Quranic verse exquisitely captures the essence of one's prohibitions in a nutshell.
Say: my Lord has only prohibited shameful deeds / lewdness (Arabic: Fawahisha), whether open or in secret; sins and oppression without right or reason and that you associate partners with God for which He has given no authority; and that you say things about God of what you have no knowledge.