Yes, I know, its Monday morning, but at 21.48 yesterday when OP was writing. I was realising why I had felt slightly lack-lustre all day. I was definitely going down with a winter bug.
A good night's sleep later and I know I have one of those vague winter bugs. No particular symptoms, just feeling really weak and wimpsy, slight headache and no energy. I will test for COVID but I am fully vaccinated and had the wrteched virus in September.
Only thing to do now is have a hot bath and have, what is own in this household, as a 'track suit day'. I have already emailed my Tai Chi tutor to say I will be absent from today's class.