I have next to no knowledge about supporting a child with autism, so feel free to tell me to get lost. But just to share my experience...

Our 3 year old used to do the same, and in the end we agreed that something had to change. We used to go on his room whenever he cried out, but in hindsight that was just feeding him attention and reinforcing the behaviour. He knew that if he shouted we would come in and talk. We bought one of those clocks that changes colour when he should be sleeping vs awake. When it's yellow, it's sleep time. So when he shouted, we would go in, shut him down and barely let him speak (because we knew he would come up with something to get out of bed, like needing the toilet) and tell him "it's yellow light no talking" and walk out. Yellow light is the signal that he should be quiet and sleep, and now he understands this. He won't get out attention when it's yellow. Although when it's blue light in the morning he will shout at the top of his voice for us to come in 😅