UPDATE - I'm excited to be able to post this update. Darus had the same behavior pattern the very next day. I was able to videotape it and brought it to his neurologist who assured me that this was not seizure activity, as I had feared, instead, it's stimming.
3:35 AM - I went into Darus' dark room after waking from hearing him kick the wall (I think?) He didn't seem upset. He was a bit warmer than usual and was a little bit sweaty, not too bad. He seemed to somewhat acknowledge my presence. I laid down with him. In a 5-10 minute span, his left leg seemed to flex/lock up and he would concurrently grunt and had a different than normal breathing pattern ... it would last for about 5 - 10 seconds. I couldn't see his eyes or face, but from feeling them, I do not think his face was locked up ... after this happened a few times he farted ... so, not sure if this was just gas? I tried to hug him a few times and attempted to bring him out of his room, but when I did, he got upset and seemed like he wanted to stay in his bed. I laid with him another 10 minutes or so and he went back to sleep.
Ever since receiving his dx, I have been on heightened alert for seizures. Per Wikipedia, approximately 27% of PMS kids have epilepsy. I talked to the neurologist this morning. She didn't seem too concerned, but we're both glad to be having a sleep study/24 hour EEG next week at UCLA.