Is it shyness? I was a very shy child, and my default answer to almost every question I was asked was no. Its due to fear. My self esteem, and more importantly my self awareness, was non-existant.
At around age 30 I started to realise this, and it made me very depressed. I had a desire to change things but didnt know how. I got help in the end. The desire for change overcame the desire to do nothing.
Having children, then getting divorced and being a single dad, forced me to look after those two little people and it changed me massively. I discovered I just dont like doing things on my own, I like company. I think thats the shyness again, almost like i feel safer in a group, even if its just with my own kids.
I still get the desire to do nothing quite often, and sometimes thats what I do, but other times I force myself to do something. In the last 10 years, as well as looking after my kids (holidays, days out etc), I reached grade 4 piano, hike a lot with a group i met, learnt to scuba dive (although may not be able to continue that hobby unfortunately), got fit on a mountain bike, met new people from the dating sites, improved my wardrobe.
Life has to have a purpose. Having children changed me hugely and i would suggest finding a way to plan for that path, even if you dont quite like the idea.
Despite all the above Im still very shy, quiet person, not much of a talker and quite boring for other people to be around especially 1 to 1. Its just how i am.