I've noticed this for a while with mine (both females!) Both fairly placid, well-behaved cats but one in particular becomes slightly agitated and won't settle. She'll sit next to me chunnering away, swishing her tail and generally looking very disgruntled - it lasts for a day or two then she calms down again. The other one woke me up at 4 this morning miaowing persistently in my face. I established she wasn't hungry, thirsty or needed the loo - she just wanted to talk she was unceremoniously chucked out though
Can't be a coincidence surely, unless I'm the mad one? 