Take a look at
this page.
You can download and scan your system with Avast (if you need one, it's a good free AV app) but the actual info I wanted you to read is "How to stop Mac programs and apps from opening on startup" section!
Check to see if there is anything unknown/unwanted and disable them.
Also check the "Applications" panel to see if there is anything unknown/new (sort by date if needed).
That should get you going until someone comes up with better assistance.
Hope this helps!