Another commenter pointed out that if you induce this through repetition it’s called semantic satiation, but the more general case is known as jamais vu. It sounds like yours isn’t caused by semantic satiation. Brains are weird and often do things like this for completely benign reasons or no reason at all. Having said that, Doctor Google (who we all know not to trust) suggests causes can include epilepsy or migraine.

In any case, it might be worth looking into, if it’s something that’s causing difficulties for you. In general if it’s some specific medical cause a neurologist would be the relevant specialist but your primary care physician or general practitioner would be your first port of call and might be able to recommend further course of action.