Having trouble starting car after sitting there over-night?

hello. A month ago, my honda civic (2000) wouldn't start after sitting a few hours. My engine light came on and they hooked up the computer and it said it was possibly a timing belt or that sensor. Well, the sensor is in the distributor and the mechanic said it was the distributor that needed to be replaced. did that and it worked fine for about three or so weeks and then i would notice occassionally for the last week that it would take a second or so longer than it should to start up - just enough for me to notice something may not be right. but I thought maybe it was related to the new part. this morning though it wouldn't start for like 30 seconds. It started fine after I got it started that first time and there are no lights coming on to indicate something it wrong. But I know somethings not right. I've already placed the fuel filter a while ago so it's not that. Any other suggestions?