My cat is about 8, had her since she was a kitten she has always sporadically sicked up a bit. Hair balls, grass in saliva, the usual. 
Last month or so she has done this more like once a week. She seems healthy apart from this, no odd behaviour, eating and drinking as usual. She will only drink from a running tap and won't touch water in a bowl I dutifully oblige to her quirk. 
Do you think I should be concerned? Should I take her for a check up or would I be wasting the vets time? And why oh why can't she be sick on the lino instead of the carpet?!?