Do you periodize your training or do you try to do the same thing all the time with some minor variations?
I'm usually tired in the fall, but in the past it was largely because of the end of summer's field work when I didn't run. I'd recover then start my base for the year (yes, in Alaska winter), then have to drop off in spring when field season kicked in again. That (combined with some foot/ankle issues) is largely why it took a while to build a decent base.
But that pattern still holds - change in seasons - although now I'm retired. Summer running is on dirt trails, generally without weather interruptions. Recover after last race (this past Sat for me), then rebuild. Depending on snow conditions on trails in winter, I may snowshoe run or xc ski. If snow is hard or non-existent, I just regular run. I'll also do a winter xt class for strengthening feet / ankles and an assortment of other things. The weeks that I do that, that gives me one hard workout in warm, brightly lit environment. Other runs may be in daylight (since I retired) or by headlamp, which is actually fun on snow. (I do like the winter feet/ankle strengthening because by the end of summer, I can feel my running getting ahead of what my feet/ankles can support, esp. if it's loose rocks. So there is a valid reason for my periodization.)
Since I've been retired and can run year round now, it definitely makes a big difference in how much base (still only high 30's mpw) I can build and confidence, which results in greater enjoyment when I'm out there running.
"you just can't pay me to care about running"
In that context, just a thought, but why are you running rather than, say, mtn biking or skiing or swimming or lifting or ....? For many of us, running is play, esp. on trails. Yea, I'd never exercise as hard as I play.
Two things I'd look at is greater change in what you are doing (periodize by seasons) and maybe considering why you run.
And if you live some place that doesn't have snow in the winter so you don't have the diversity that some of us get to enjoy, well, sorry, I can't help with that. But maybe there is something you can find that works for you in this period where you don't normally run.
Good luck.
