What a coincidence, I experienced this for the first time when falling asleep a week ago. It was clearly inside my head, so first I suspected it was somatic and

What a coincidence, I experienced this for the first time when falling asleep a week ago. It was clearly inside my head, so first I suspected it was somatic and was quite worried. Some quick googling and I found the hilariously named "exploding head syndrome". Possibly related, I occasionally get "brain zaps", spontaneous sensations of an electric shock inside my head, also when on the verge of falling asleep. These are almost exclusively described as a symptom of SSRI withdrawal, but that is interestingly not the case for me.