What's up with Ozzie?

I still haven't figured Ozzie out. I put the boyz to bed about 10:00 p.m. every night. I join them around 11:00 p.m. Most of the time they don't wake up when I come to bed and I usually do not have to take them out to potty until around 2:30 a.m or so. Anyway, Ozzie was standing there trembling like he was scared to death when I came to bed. I went ahead and took him out to the yard, where he proceeded to be his old self. He did his business and communed with nature until I had had "enough of the mosquito bites already". Of course he had to make me chase him all over the yard to get him to come back in and go to bed. He still wouldn't settle down. He marched up and down the bed, whined and would lay his head on my neck or chest, but would not lay down and relax. He would still be standing up with his head on my chest. Finally, I fell asleep and when I woke up later in the night he was sound asleep. I'm sure he was exhausted. Hopefully he will sleep tonight. I am beginning to wonder if I should take him to the vet.