Hmm, I'm sorry that you had that experience. I don't believe it is common from ambien. Ambien is anxiolytic; it tends to relax anxiety instead of cause it. But the effects of ambien can be confusing and I can see the confusion turning into anxiety or paranoia under some circumstances.

So you had the experience. Do you have anxiety or paranoia at other times? Perhaps what the doctors call Generalized Anxiety Disorder? Try to keep your thoughts relaxed during the day / in general.

Perhaps it was the feeling of being awake but under the influence of the drug. So maybe something was keeping you up like caffeine or sleeping too early / not tired enough even with ambien.

Avoid caffeine in the afternoon and take the ambien right when you get into be / don't stay up / try not to be awake on it if you are using it for sleep.