I am sorry you and your glider are going through this.
There are many possibilities but his symptoms sound serious enough that you really MUST take him to a vet to get the diagnosis and medical treatment he needs.
If taking him to a vet is not an option, you may only be able to keep he comfortable as he goes down hill.
It sounds as though he had a seizure which could be from many causes including low blood sugar or low calcium levels. It could also be due to coming in contact with something toxic.
Only a vet can give you the correct treatment to save your glider's life.