Strange thing I have experienced lately. I readied a starter for brewing with an old smack pack of American Lager. MFG date was in April so I knew it would take some time to get going. I had a 2L starter going for three days on a stir plate with no activity at all. I then placed the flask in the fridge for a day and in the evening placed it back on the stir plate. This morning there are signs of active fermentation. Now this not the first time I have seen this. It's happened three times and it's become part of my process now of the starter does not take off right away. I am wondering what is causing this, maybe crash cooling and warming the yeast up is getting them active again? Anyone else ever see this?