windshield wiper initial delay

I have a 1998 honda accord LX and my windshield wipers don't start immediately when I turn them on. They used to start right when I turned the switch on in the morning. Now there is an initial 15 second delay before they start moving. At first I thought they had frozen to the windshield, but I lifted them up and they weren't stuck and still didn't move. Then a several seconds later they started to move. I've tried all positions... delay, slow, fast... but regardless of position there is no movement at first, then after the initial delay they work fine. After I drive along for a few minutes if I turn the wipers on again there is a brief delay of about 2-4 seconds before they start. I tried them when I got in the car this afternoon at lunch time, and the delay was short... 2 seconds... unlike the longer delay first thing in the morning. Could it have anything to do with the cold (gets down to the high 30s at night around here in northern california)? Is the motor or a relay going bad? Once the wipers start working they work fine. They always responded immediately whenever I turned the switch on up until about a month ago. Any ideas what is causing the delay and how to fix it? I don't want them to totally fail on me sometime in a rainstorm. Any suggestions would be appreciated. thanks.