What can cause a sluggish start?

I have a 85 Caprice Classic and on the 1st start of the day i have trouble starting. I turn the key and the engine cranks, but it wont turn over. Once it heats up, it starts rite away, everytime. But that 1st start of the day, ill have to try 3-4 times, and it slowly gets going. 3weeks ago It started up fine, then i would have turn the key twice n it would start on the 2nd time, then i had to do it 3 times, now 4. Could it just b the spark plugs? Keep in mind, it only does it on the 1st start of the day. All other starts during the day it starts rite up and its different then when the carb is cold needs to warm up, i know how the car acts then.