I was in more or less your position just over a year ago.
I used to be a reasonable cyclist in my late teens/early twenties, then I learnt to drive
The Black Dog™ got hold of me about 4 years ago and slowly cut me off from the world, had to give up work, the house, the car, basically everything. I'm still out of work but cycling is helping me get back to some sort of normality, god knows the drugs didn't work.
I too like it quiet, I went out for a trial run with my local CTC group a while back and as nice a bunch as they were I just can't deal with groups of people so it's not for me.
My only advice would be to not really set any goals or have any preconceptions of what you want to achieve, just go out when you feel like it and enjoy it, forcing yourself out of the house because "you've still got 15 miles to do this week" is sure to have you loathing it in no time.
It 100% has to be something you look forward to and not something you have to talk yourself into.