Sounds like TBE (toilet bowl effect) to me. Do you mean with the nose always facing say north, the heli will slowly spiral around in a circle with the nose always facing the same direction? Was the heli new in the box, or just new to you? Has it been crashed? Lots of things to bend and get out of whack on a heli that can all lead to TBE. If it's been crashed at all try this test.
Check for either a bent inner or outer shaft. Hold just a little throttle until the blades just start to turn then hold full left rudder and check for any wobble in the shaft now do the same with full right rudder and check the other shaft both should be smooth any wobble will cause the dreaded toilet bowl effect.
Also check to make sure your flybar is balanced, and that the blades aren't too tight. If the blades are too tight to move freely in the grips, this can cause TBE as well. Let us know what you find.
