Engine periodically just turns over fine but doesn't fire. Later starts OK.

What is your question?

Has happened any time of day-6am-9am-4pm. (at home almost daily) Then has started in 10 or 20 min. or 90 min.--or?? Sometimes sputters like it's trying to start but doesn't. 1 or 2 times it started rough then smoothed out.Has been at garage 5 days-never failed to start-nothing shows on scanner. No difference using original key (warn some) or new key.