It might be from condensation on the toilet tank. I had this happen to me and I finally figured it out. Why did I have so much condensation on my toilet tank? I had so much that it was dripping off and puddling! A little bit is normal - the tank fills up and the water in it is colder than the air so humid conditions cause condensation. To make a long story short, I had a very very small leak where some tank water was sneaking down over the top of the overflow pipe. The tank was always refilling by just a little bit. This kept the fresh, cold water coming in just enough to keep the tank water cooler than the air. With no leak, the tank water would eventually warm up and the condensation would stop and no puddling would occur. You could also have a leak at your flapper. Sometimes the leak is so small you can only hear it, or the refilling in the middle of the night. If you are very frequently flushing the toilet it could also keep the tank water cold. If this is the case try only flushing for #2, or at least not for every #1. Switching the toilet feed to hot water might help, but usually the water comes out cold right at first anyway.