Hi Char and welcome,
I also have had many episodes over the years of emotional numbing. It's been called depression by doctor(s) but my counsellor tells me it is a form of dissociation. For me it can last anything from three months roughly to six months and then not recur for quite a while. I have figured out many strategies over the years to help before, during and after an episode. When I am like this every moment of the day feels like a year and as I don't sleep well at the time as well, the nights are very long too.
During a period of this I get by by doing anything that is vaguely pleasurable - in my case puzzles or reading or whatever I can think of. I am usually in a holding pattern until I get better/figure out what triggered me off in the first place. Counselling is very important - even if I make no progress there for a while, eventually we figure out what led to me shutting down (this can take quite a while). Then I start feeling again and experiencing the pain, sadness and anger behind what has happened (in the past and the recent present). I am just starting to accept now (having had a shut down period recently through our southern hemisphere winter) that I don't mean to shut myself down but a large part of me has gotten overloaded and does not know a better way to cope. I think it was a coping mechanism from my childhood as the only way at the time to cope with an intrusive mother and various bad events.
After an episode I now try to write down in my journal as much as I can about what happened, hoping it will help me if/when it recurs again. Having some kind of support system around you is also very helpful. My husband is now good at reminding me that I will get through it, even if I find it hard to believe him at the time. I have a couple of close friends who remain supportive even when I can barely think of a single thing to say to them. When I am like this I also avoid people and generally don't want to leave my house/room. I've found that sometimes giving in to this isn't the worst thing in the world and at other times going against this feeling is very useful - so I do go out with someone close to me despite how I am feeling. Some people probably find exercise very helpful too. I think antidepressants have also helped me weather these episodes- they help keep me safe because I find being shut down very stressful and upsetting. And I don't feel like a good person when I am like this. This last episode I also found it helpful towards the end to do some structured stuff around the house - practical activities that I might usually enjoy. Even though I couldn't feel much pleasure while doing these activities I still felt better about myself afterwards than I do when I'm doing what I would consider time-wasting/purely time-filling activities.
Hope all of this is helpful. I find being able to connect with people's experiences has made a huge difference to my life, and finding this website was actually the "trigger" to leading me out of disconnection this time!