Senate Minority Leader Robert C. Byrd (D-V.Va.) has invited his Democratic colleagues to a weekend "retreat" at a West Virginia resort to discuss future policies and directions for their party.

The session to be held Oct. 2-4 at Canaan Valley State Park is viewed by some senators as an effort by Byrd to re-establish his authority, which has seemed shaky at times this year, and to help the Democrats regain their bearings after the loss of their Senate majority in 1980 for the first time in 26 years.

Byrd said the weekend for the senators and their spouses "will give us an opportunity to get together to discuss issues in a relaxed atmosphere. The press of Senate business and the constraints of our individual schedules do not allow us time to discuss in depth the issues that confront us in 1982 and beyond in a more or less private setting where we are not interrupted by quorum calls, phone calls or committee meetings."

The idea of an informal weekend for the senators was reportedly suggested by Sen. Daniel Partrick Moynihan (D-N.Y.), an admirer of the Tidewater Conferences for Republican elected officials hosted by Sen. Bob Packwood (R-Ore.). Those conferences, held each spring in Easton, Md., are open to Republican senators, representatives and statewide elected officials.

Byrd said the idea of such an informal weekend roundtable got an "enthusiastic reception" when he suggested it to the Senate Democrats at their caucus. He said the format was still unsettled but added, "We might invite a few outside experts" to join with the group to stimulate discussion.

He said he was sure there would be "some press coverage," but how much of the session would be open was uncertain. The Tidewater Conferences have been open to full press coverage.