Greetings!

Did you inherit this UAT server or build it yourself?

Before going mad just restore it elsewhere, if successful and the result is a perfect copy of production, you can rule out any troubles in production and focus on the one UAT server. <-- how much time do you wish to waste if its the UAT server or are you determined to find out what's going on?, how long to rebuild?

Have you run dbcc checkdb on a restored copy on the UAT server?

Offlined sql and run check disk at the os level?

Maybe run a profiler trace on the restore?