Losing interest in the hobby
I think everyone sooner or later has the same feelings. If you are not excited about your cars then your not excited, no reason to explain or apologize. I've had some cool interests that I did for a year or two and then went onto something else ( for example I had a NACRA catamaran and at different times sea-doos & Kawasaki jet skis.)
My advice is to take a break and don't do anything too drastic too quickly - like sell all your cars.