Starter clicking

Hi, I buyed my 850xp eps 2011 on friday. My atv is always sleeping outdoor. This afternoon I've tried to start my atv and I just heard a clicking sound when I turn the key. So I removed the front rack, I've checked the battery poles, it was a little loose, I've tighten the 2 bolts and shake the wire. After that, I've tried an other time, I heard a clic and it start. So what do you thing it could be...bad starter, bas selenoid?? thank!