これかな？
こいつを_vimrcか、.vimrcに書いておけばよい

" When editing a file, always jump to the last known cursor position.
" Don't do it when the position is invalid or when inside an event handler
" (happens when dropping a file on gvim).
autocmd BufReadPost *
\ if line("'\"") > 0 && line("'\"") <= line("$") |
\ exe "normal g`\"" |
\ endif

augroup END