With these adjectives, I don't think it makes any difference.
He was a nerdy, dumb, shy guy.
He was a dumb, shy, nerdy, guy.
He was a shy, nerdy, dumb guy.
I was actually asked this question but since I had no clue if there's any order for the adjectives I thought I'd better share it here. I know the adjectives (and even why one might want to use them in a row!) sound ridiculous, but please let me know if, as a native speaker, you prefer to say them in any particular way.
Nerdy, dumba**, shy, are the adjectives he wanted to use for a person! (I'm so sorry for the adjectives...!)
Thanks a lot!
By the way, is there any such general rule as the following one? [I just heard it from a friend, but don't know the source he consulted.)
1. General opinion/judgement 2. Physical characteristics 3. Mental characteristics
It's OK, but I wouldn't take it as a rule- you will find other sequences being used. These things aren't written in stone.