The urge to do nothing at all

In the last 15-20 years I have always had this urge. I think it tends to be dependent on how stressful the months or years preceding this urge has been prior to having it. It meant that when I was ill, physical illness such as a cold or flu, I embraced it, the chance to hide away in bed, sleep and stay hidden with the excuse of being ill and contagious. 
'Sorry, can't go out I'm ill.' 
Easy. 
When it came to the mental illness, well I think I've covered that one before.
But the more I've thought about it the more it has become clearer to me and that is those urges were borne out of need for self care before a big depressive episode threatened to overwhelm. Which, of course, is exactly what it did. It has been on my mind because it is threatening now and I think, or rather I am hoping, that this is more down to the time of season, the colder wetter days, the darker evenings. That urge to hibernate away is always strong around now. But is it that or is it the other? That grey mass that hovers over the horizon and bodes towards a blanking out the blue sky. I'm just not sure and that is what worries me.