I think I have been experiencing this. I know my daughter seems to think I should not be overwhelmed, as I do not work or even get out much. Just the thought of making the trip to Portland to see my grandson can feel overwhelming, even though it is something I greatly enjoy. I rather hate the feeling that I am becoming inflexible (like sleeping in my own bed, need my familiar surroundings to feel comfortable, etc.) because just ten years ago I loved adventure and welcomed challenge and difficult tasks. It was just 13 years ago that I was camping in the snow in the Olympics for a week-end, hiking the ridges and helping a friend trim trees for the forest service. And 15 years ago I was climbing mountains. And now going shopping is something I often have to psyche myself up for!

But sometimes, like you say, there is no trigger for the feeling of being overwhelmed. It just comes on like a chill, or tiredness.