I have lived with what I call The Evil That Lives Within for a long long time now. It strikes when least expected, but rears its ugly head more frequently when I'm tired. Which I am.
It tends to start with the lower back and backs of the knees both feeling incredibly weak and strangely numb. Then the dizziness, breathlessness, indigestion and long sleeping sessions. Lasts a few days and then back to normal, if I can ever be described as that.
The world is falling apart, and my body's not much better. No, not old age, just me.