I'm not saying this is what's up with your machine, as you said it did run fast. But it's always worth a try:
dmesg | grep -i error
dmesg | grep -i fault
dmesg | grep -i bug
dmesg | grep -i not
And whatever keywords you can think off that may lead to useful information.
You can do the same with
cat ~/.xsessionerrors | less
cat ~/.xsessionerrors | grep -i error
... and so on...
Because an erroneous machine is a slow machine.
If this yields some info, you can get a closer look at those messages by adding the 'C #' flag to grep, where # is the desired number of lines of context. For example:
dmesg | grep -iC 3 error
Gives each find three lines of context. You can make more sense of this by adding the --color=always flag. The complete command would be:
dmesg | grep -iC 3 --color=always error
If you find the --color=always flag useful, you can add this to ~/.bashrc to activate it by default:
alias grep="grep --color=always"
And of course see what's eating your resources with
For now you have homework enough :-p
Questions, answers, opinions, suggestions, side notes and remarks are welcome