Welcome. If there is such an internal timer, I'm not aware of it.
But this is the first time the question has come up.
There is a self diagnostic/reset procedure; if the mixer boots up without message or issue, and machine's functions are all normal (and there are no missing parts, trashed pieces, or obvious signs of abuse), it's probably a good mixer.
My suggestion: if you can't inspect in person (ideally with a knowledgeable user), ask LOTS of questions. Make sure what you're buying is what you'll be getting.
CaptDan