CL30 flight crew reported receiving a terrain warning during approach to an airport at night. The crew leveled off and resumed the approach once the warning ceased.

Narrative

Descending into ZZZ on a downwind leg passing roughly 2400 feet just as we were about to turn for a little more than a 5 mile base we received a caution terrain I called out the warning Person A started to stop the descent during that time we received an momentary terrain warning as Person A disconnected the Autopilot bringing the nose up. The terrain display was up on both of our Primary Flight Display (PFD) and no yellow or red displayed. once we were clear of warnings and leveled off no further conflict existed and finished landed without incident Cause: I believe that because it was a later night flight and we out of our typical sleep cycle our situational awareness was lower than normal. our descent rate looking back was a little higher than normal which was result of the delayed descent into the airport which could have caused the warning. Suggestions: Knowing that we are all at a level of fatigue that effects our situational awareness setting up and asking for the full approach would have been a better course of action.