Post-regenerative amnesia

Post-regenerative amnesia was the loss of memory which was a common-side effect of Amnesia traumatic regenerations. Symptoms ranged from uncertainty about names, (TV: Castrovalva, Time and the Rani, Deep Breath) including their own, (TV: The Woman Who Fell to Earth) forgetting a skill they had mastered, (TV: The Time of the Doctor) or complete memory loss. (TV: Doctor Who)

The Twelfth Doctor suffered a brief memory loss immediately following his regeneration from the Eleventh Doctor. The most immediate concern was that he forgot to fly the TARDIS, (TV: The Time of the Doctor) leading it to land inside a tyrannosaurus rex which was deposited to Victorian London as a result. Disembarking, the Doctor initially failed to recognise his companion, Clara Oswald, to the point of mistaking her for Handles. (TV: Deep Breath)

The Thirteenth Doctor was initially unable to identify herself. However, following a confrontation with Tim Shaw, she was able to remember that she was the Doctor, observing that "a bit of adrenaline, dash of outrage, and a hint of panic knitted [her] brain back together." (TV: The Woman Who Fell to Earth)