My set ai command in the vimrc file isn't working - vim

Question

I am new to vim. I have written my default settings in the vimrc file. My vimrc file has been given below. In that file I have written set ai command for auto-indentation. But it isn't working. I have to write the command every time I start working on vim.
I also have a plugin vim-indent-guides installed. I want the command IndentGuidesEnable to be run when vim starts. But I am failing here also. What I am doing wrong?
call plug#begin()
Plug 'chriskempson/base16-vim'
Plug 'scrooloose/nerdtree', {'on': 'NERDTreeToggle'}
Plug 'scrooloose/syntastic'
Plug 'tpope/vim-fugitive'
Plug 'tpope/vim-surround'
Plug 'bling/vim-airline'
Plug 'majutsushi/tagbar'
Plug 'scrooloose/nerdcommenter'
Plug 'airblade/vim-gitgutter'
Plug 'valloric/youcompleteme'
Plug 'pangloss/vim-javascript'
Plug 'easymotion/vim-easymotion'
Plug 'vim-airline/vim-airline'
Plug 'godlygeek/tabular'
Plug 'honza/vim-snippets'
Plug 'ervandew/supertab'
Plug 'tpope/vim-repeat'
Plug 'mattn/emmet-vim'
Plug 'nathanaelkane/vim-indent-guides'
Plug 'shougo/unite.vim'
Plug 'terryma/vim-multiple-cursors'
call plug#end()
set number
set paste
set runtimepath^=~/.vim/bundle/ctrlp.vim
set foldmethod=indent
set foldlevel=99
set tabstop=4
set softtabstop=4
set shiftwidth=4
set textwidth=79
set expandtab
set fileformat=unix
set ai
set list listchars=tab:→\ ,eol:↲,nbsp:␣,trail:•,extends:⟩,precedes:⟨
nnoremap <C-J> <C-W><C-J>
nnoremap <C-K> <C-W><C-K>
nnoremap <C-L> <C-W><C-L>
nnoremap <C-H> <C-W><C-H>
nnoremap <space> za
autocmd VimEnter * NERDTreeToggle .
autocmd VimEnter * IndentGuidesEnable