Put yourself in a position that will keep you awake and don’t worry about it. The ego is the part of us that uses words to describe reality. When you move into another part of yourself that does not use words, it can feel like falling asleep. The ego is not the part you are strengthening during meditation, so if it checks out, don’t worry about it. Your higher self in doing it’s thing and who really cares what the dumb, endlessly negative little ego thinks about anything.