Sometimes the police will gather information that will make them suspicious of your condition independent of your driving habits that evening. The cases in Ohio go both ways on this one.
In one case, a police officer was found to have Reasonable Suspicion after seeing a person drunk in a restaurant, and shortly thereafter, seeing that same person driving his car flawlessly. State v. Bycznski (1994) 98 Ohio App.3d 625; State v. Malco, 2000 Ohio App. LEXIS 901 (March 10, 2000) Montgomery Co. App. No. 17817, unreported.
But in another case, the court of appeals reached a different conclusion of law finding that observations of an officer before the suspect drove did not constitute Reasonable Suspicion for the stop. Berea v. Sarrett, 1998 Ohio App. LEXIS 3154 (July 9, 1998), Cuyahoga App. No. 71931, unreported.