Suffering from can't be arsed syndrome means you can't be arsed
to do anything. A general lack of motivation to do basic tasks. Taking it easy. Avoiding heavy work. Finding day to day tasks cumbersome. Used in an specific instance as an out of the ordinary day for someone who is usually hard working.
dude 1: I am suffering from can't be arsed syndrome today.
dude 2: Why? What's up?
dude 1: I just have no motivation.
dude 2: Are you tired?
dude 1: Not really. I just can't be arsed
dude 2: I know what you mean.