Delamination
Not everyone experiences their thoughts in conversational speech, but I do. A complete thought, for me, consists of a few different components: the final formulation of the thought in inner speech, preceded by an immediate intuitive grasp of the content of the thought. The inner speech version of the thought is slow and wordy compared to the intuitive thought, but isn't usually something I perceive as a separable component that I could stop doing. They're both part of the thought, like layers of a laminated sheet of paper.
There have been times in my life where that paper has become delaminated. Usually there's some severe stressor or physiologic derangement involved (illness—physical or mental, extreme sleep deprivation, or certain drugs such as pseudoephedrine). The contents of the thoughts are still recognizably my own, but the intuitive component which initiates the thought does not feel owned by me. It feels alien, as if I'm operating a relay station, receiving signals from another source, and then just passing them along, by translating them into language. The last step isn't obligatory, but it's what 'reclaims' the thoughts, makes them feel 'owned' by me again.
Another point to make, in addition to the missing 'ownership' of thought, is that the intuitive immediate component of thought becomes an object rather than a seamless part of first-person experience. This lends itself to a certain kind of hyper-reflection where my own thoughts are almost as prominent as real external objects.
I feel like there's always a risk that by introspecting or being mindful, I will slip into this state again, and that the consequences of doing this will be inherently mentally destabilizing. The last time this happened, it was the herald of a peculiar severe depression. Realistically, I doubt that this kind of introspection actually causes mixed depression, but they're now closely associated enough that I would like to stay some distance away from paying this kind of attention to the form of my thoughts.