“自言自语”常见的英文表达是 “talk to oneself” 或 “say to oneself” 。
talk to oneself：强调发出声音的言语行为，更侧重于实际开口说话这个动作。
例句：He often talks to himself when he is thinking.（他思考的时候经常自言自语。）
say to oneself：更侧重于内心的独白，不一定有实际的声音发出，强调心理活动层面的“说”。
例句：She said to herself, "I must do better next time."（她自言自语道：“我下次一定要做得更好。” ）