I'm thinking he just wants some comforting feeling and sometimes when he's moving around I rarely get any sleep as in none or just a little bit.
I do want him to feel comfortable but I also want myself to feel comfortable too.
My children both come into our bed from time to time. We used to co-sleep but transitioned to having separate bedrooms about a year ago. They now sleep in their bedroom and we sleep in ours. However, I still spend a lot of time comforting them in their bed and they still come to our bed fairly frequently. So, sleepless nights are not that uncommon although not as many as they once were. I would try to comfort him in his bed and see if that is enough before allowing him to come into yours if his being there means no sleep for you.
Would your son be happy with you sleeping with him some nights?
I have two soon-to-be eight year olds. We have full-sized beds in each of the children's rooms and in our room so three or four in a bed results in a crowded sleepless night. We switch it around every night. Some nights they sleep in their own beds and my husband and I sleep together. Other nights, my husband sleeps with one child and I sleep with the other. Other nights both children sleep together or I squeeze in the bed with both children and my husband sleeps alone. Each night we decide as a family who is sleeping where. (Sometimes on the weekend we 'camp out' all together on two air mattresses in the family room.)
It sounds like a mess but it works for us.
I think its perfectly reasonable to want your eight year old to sleep in his bed. When our eight year old comes to our bed, we take him by the hand, take him back to bed, tuck him in, kiss him goodnight and we leave. (we have two other kids, a 1 year old we are co sleeping with, so our bed is not an option) and really little by little he stopped coming. We do cuddle with him at bedtime, read, we talk, its a good 35 minutes of one of us just with him and we remind him that he needs to sleep in his bed. We also got him a stars at night thing that puts stars on his ceiling and that really helped.
Or you could look at particular times of night if that helps. My kids are in their own beds, but I lay with the younger until he falls asleep many nights; and I do that with the older if she's been having nightmares or trouble getting to sleep. I don't mind doing that for half an hour while they fall asleep!
And they have a time in the morning when they are allowed to climb in our bed as well. Before that, they have to play quietly and can get snacks in the kitchen. Generally, either DH or I will get up and supervise, but the kids aren't allowed in our room until at least 7:30. The older kid can tell time, and the younger can at least read the numbers 7:30 on the clock. We do sometimes get the 7:03 wake up instead, but I can live with that.