I just went though this! After ruling out obvious things would go to plans B, C and D. Hubby loved Christmas, so I hooked up the Netflix and played the Rockets Christmas show. That worked a few times. Other times, I would just rub his head. This is something he enjoyed before he became non verbal. Yes I did a few times resort to his medication, if nothing else calmed him. Good Luck!
My grandma does this. She does this when she's bored, doesn't like to not see people in her vision at all times or needs something such as water or to go the bathroom. A walk around the house including a bathroom break sometimes will distract her enough to make her stop for a little while. If that doesn't work, we do her finger nails, look at photo books, talk to her, give her something to munch on (as sometimes its just shes hungry it appears), lotion her hands and arms, or read her a book. I have found it's often that there is an underline issue with her but sometimes there is not. if you have exhausted all other avenues, I'd just turn the TV up a bit or spend time in another room.
Cwillie has great ideas. My mom does this and I can usually sooth her by just gently telling her I am here with her. I will stay. Sometimes applying lotion to her hands, arms, legs is soothing. Or I will put her and sing to her. It is a lot of trial and error when they no longer are able to communicate their needs.
Sometimes you can figure out what the problem is by playing twenty questions or checking the obvious. Pain? Change of position? Hunger? Thirst? Toilet/diaper change? Boredom?
Sometimes there is no clear cause, it is just a totally meaningless vocal tic or fear and agitation that can't be soothed. Distraction can sometimes help with that... change his position, put on some music, take him for a walk. There are medications that can help too, but it may take experimenting to find something that works without zonking him out. If all else fails put on some headphones or get busy in another room so you don't go batty.
Sometimes there is no clear cause, it is just a totally meaningless vocal tic or fear and agitation that can't be soothed. Distraction can sometimes help with that... change his position, put on some music, take him for a walk. There are medications that can help too, but it may take experimenting to find something that works without zonking him out. If all else fails put on some headphones or get busy in another room so you don't go batty.