Delayed Onset Energy Disorder, known as Delayed Onset Ki Disorder (遅発性乱気症 Chihatsusei Rankishō) in the Japanese version, is a disorder that greatly hinders a person's Ki.
This rare condition is the result of using one's ki in a reckless or excessive manner, and presents its symptoms a few days after said usage. As a result, the users ki is greatly affected and only a fraction of the user's ki is able to be used. It is unclear how long it takes for it to heal, but the disorder will eventually cease in time. King Kai noted that if Goku continued to use his ki in a reckless way, he would not be able to become stronger, which greatly worried him.
In Goku's case, he was suffering from this disorder due to his usage of the X10 Super Saiyan Blue Kaio-ken in the Tournament of Destroyers. Due to this disorder, Goku could barely control even a fraction of his ki, and has stated to Piccolo that if they were to fight all-out, Goku would lose. This disorder also affected Goku's flying, as he had unintentionally crashed into his house, destroying it. This disorder also affected his Instant Transmission technique, as it took Goku at least 4 tries to teleport to his intended destination, which was King Kai's Planet. It is also worth mentioning that even though Goku's appetite is normally abnormally large, this disorder greatly reduced his appetite, as it worried Chi-Chi and Goten that Goku ended up eating less than half of his daily food intake showing it can reduce a pure Saiyan's normally large appetite indicating it may also slow down their metabolism.
King Kai is shown to be knowledgeable of its symptoms which in Goku's case were triggered by his reckless use of Super Saiyan Blue with the Kaio-ken that King Kai himself thought up and developed. However Goku apparently took King Kai's advice as he never suffered from the disorder indicating proper training can allow a God-like Saiyan like Goku to utilize even a X20 Super Saiyan Blue Kaio-ken during the Tournament of Power without suffering from said disorder indicating it is triggered by the reckless use of ki by one without the proper physical training to handle the strain caused by such reckless and excessive ki manipulation.