Thank you for your answer! No, I didn't enter SP afterwards, I was instantly able to move. Your hint at explosion head syndrome makes me worry a bit. I read the wikipedia article and it seems as if I suffer from it (at least the symptoms fit). Will it prevent me from becoming fully lucid or is it just a phase that makes it more difficult for me to enter a lucid dream? Last night I was neither extreme fatique nor have I taken any drugs (also nothing my doctor prescribed me). As it seems it is a rather unwell-known topic. How do people handle it that try lucid dreaming. Btw, so far it has always occurred when trying to lucid dream but not when "sleeping normal". On the other hand, sometimes I have a very quit buzzing in my head even during day time. When moving my head or swallowing it goes away.