When your laptop is sleeping, it can't be doing computation. I mean, that's not specific to LLMs. You're going to have to set it in your OS to not sleep.
The only exception I can think of would be if you (a) have it connected to wired Ethernet and (b) the laptop can do Wake-on-LAN; in that scenario, you could rig something up where it wakes up when something tries to contact it. In practice, you probably just don't want to have it sleeping.