How do I repair or erase a late 2013 iMac's hard drive in recovery mode while reinstalling macOS Catalina?

i'm running catalina on a late 2013 imac because i prefer using iTunes instead of the new music app.

it was running fine but has now begun to restart itself after a couple of hours. i tried re-installing the OS through recovery mode but it didn't solve the problem.

i suspect the hard drive might need to be erased or repaired. if i choose that option in recovery mode will i still be able to re-install catalina? should i repair or erase?

thanks.

bruce