Since we don't know what you have and what software you use regularly, it is difficult for us to say. However you could look up the starttup items at

http://www.castlecops.com/StartupList.html

which gives advice on whether a startup item is definitely needed (e.g. you antivirus software), user preference, or bad (malware).

Many apps that set a component to load on startup have an option to disable it, so when you find out what a particular item is you could check the settings in the corresponding software and disable it from there.