Personality Disorders Support Group
Personality disorders form a class of mental disorders that are characterized by long-lasting rigid patterns of thought and behaviour. Personality disorders are seen by the American Psychiatric Association as an enduring pattern of inner experience and behavior that deviates markedly from the expectations of the culture of the individual who exhibits it.
Also not sure if you are aware of the symptom of disassociation in bpd, which if you have been diagnosed is more likely to be the cause. This usually happens at times of extreme stress or emotion. You may appear to your friends and loved ones as 'zoning out' or 'glazing over'.
I should keep in mind, though, that sometimes these experiences are similar to a "flow" state, which is supposed to be an optimal state in which one is so engaged in a challenging activity that they lose sense of self. But THAT is a constructive experience and one which people enter intentionally. Have to figure out how to come back to myself when it's not so functional, but I haven't yet come across any strategies for that.