If you want to identify what is causing it, you could try a clean boot, i.e. disabling all startup items and third-party services and re-enabling them one by one to identify which is introducing this cmd. Note that this is a temporary solution because once you install new software they may introduce this cmd pop-up you see and you're back to square one. Another note, you may have to disable multiple services/startup items. On my old laptop there are up to 10 cmds showing up at startup.
I agree with britechguy that there is nothing to fix here because it's normal behavior. If you want to address it regardless then open task manager (press ctrl + shift + esc keys simultaneously, this is a shortcut), go to startup tab and disable all items. Next in msconfig (press Windows key + r, type msconfig and press enter), go to services tab and check Hide all Microsoft services (important! Accidentally disabling a Microsoft service could prevent Windows from booting) and uncheck all other services, now reboot. From there enable one service or one startup item in task manager and see whether a popup occurs. Enable a new item then reboot and see whether a popup occurs again, continue this until all items/services are enabled again and note which service/startup item shows the popup. As britechguy mentions you may not always see them so you may have to repeat this process a few times.
