It would be great to have an option in Parallels Desktop to automatically suspend VMs after a configurable amount of time that the host Mac has been inactive. My reason for this is that I leave my Mac running all the time and occasionally return to it to find that it has restarted after a kernel panic. Obviously when this happens any VMs that I left running have died too. The requested option would remove the need for me to remember to suspend my VMs at the end of the working day.
This is not the solution for your problem. If finding your mac has rebooted from a kernel panic is a likely possibility than something is utterly wrong with your mac, hardware or software wise, and you should look into solving that or you incur in the risk of losing your data.