While GERD could cause nausea, nausea itself is a very non-specific symptom and could result from
GI infection/ inflammation, micronutrient deficiencies,
GI motility issues, o non-
GI causes such as stress/ anxiety, hormonal/ endocrine imbalances, metabolic issues, micronutrient deficiencies, medication side effect etc. I would suggest getting this evaluated by an internist initially and depending on the cause diagnosed/ suspected, it can be managed accordingly or specialist care may be sought.