Hello Everyone!
Thanks for the responses! I posted this on a Friday night, so I wasn't able to take him to a vet until Monday morning. This is not a normal sound for him, so I kept a close eye on him, and it turns out that he was constipated.
I fed him a little yogurt and some extra cucumbers, which got him back on track. I still took him to the vet once Monday rolled around, and she said she had no clue why he had been constipated. He showed no signs of a blockage or any sort of problems. I didn't change his routine or any smells in the house or anything like that.
It seems like he just had a bad day - but it just goes to show you that you need to pay attention to all of your glider's noises! I knew this wasn't normal for him, and now that he's better he has not made it since.