Wiping an old mac and reinstalling High Sierra

Sorry if this is a stupid question, but I have an old iMac (mid 2011) which has developed kernel panic (I think it is called), where the mac keeps restarting on its own for five or ten minutes every morning until it settles down.

In order to try and resolve this, I want to completely wipe the mac and set it up as a new machine. I have backed up all my files, software, etc. and was just about to do a complete erase/clean install, when I realised the most up-to-date version of mac OS I can run on it is High Sierra - will this be a problem?

I suddenly had this thought that if completely wiping, the mac might automatically try to install the latest version of mac OS, which it doesn't support, and therefore I might not be able to complete the process. Or will it know to install a new version of High Sierra after the erase has finished?

Any help would be appreciated!