OMW… I have this exact problem... I don't even have to try/want to crack my joints - they just crack.
This is really bothering me.
Initially I started cracking my fingers/knuckles back in 1998, It's moved on to almost all my joints, but now they just crack themselves!
I'm 24 in 3 months time and I feel I just need this to come to an end...but frankly, I don't even think it's possible.