In vim I can use f followed by a character to go to the next occurrence of that character on the current line. For example, if I have the following (cursor position
f
wilhelmtell's answer will work unless 'ignorecase' parameter is set. If 'smartcase' is activated or 'noignorecase' then it is okay.
'ignorecase'
'smartcase'
'noignorecase'
However a pattern that can replace [A-Z] is \u (see :help /\u or more globally :help pattern). Therefore you can replace your mapping with:
[A-Z]
\u
:help /\u
:help pattern
:nnoremap C /\u:nohlsearch