snowtiger308

I am going to make an assumption, and often that leads to problems... I am going to assume that it has a set trigger (two triggers in the trigger guard) the rear one being the set trigger) In between the two triggers is a small screw hanging down...??? The adjustment of this screw may give you the symptoms you are decribing... and as Cayugad suggested there may be a physical problem...

Let us know what trigger and what rifle you have...