You might find you enjoy it if you force yourself to go out (if your just being lazy).
Also has this attitude seeped over to other aspects of life? If so then I would say it’s Anhedonia and that many people get it as passing phases throughout their lives, if it lasts a few months and starts to impact your life then I would suggest counselling. If you are feeling a bit ‘cant be arsed with anything’ then as other’s have said, give yourself a break and just enjoy not worrying about anything.
In some respects this is the toughest time of the year, summer (cough) has gone, the autumn colours are fading and it’s just wet and boggy. The clocks have gone back. The cold weather which firms the ground and those great frosty or snow tinged rides are a way off yet.
+1, quite literally SAD. Wouldn’t be surprised if there’s some kind of evolutionary mechanism going on telling you to slow down for winter.