In Europe, there is an almost universal belief that the economic summit at Williamsburg at the end of this month will be a dud. When they speak privately, Europeans say bluntly that President Reagan offers no real leadership to a world teeming with economic problems.

At the same time, candid observers confess that there is no European or Japanese politician who has the clout and charisma necessary to take the leading role (and if there were such a Japanese, the Europeans would rule him out, anyway). So, it is to America that all the rest look.

If the Williamsburg summit, for lack of a strong hand or sense of unity, should prove to be a flop, that of course would be regrettable. It is even possible that a serious failure could write finis to the summit process.

But in a recent series of meetings and interviews in Europe, I sensed a deeper frustration about the deterioration in relationships among the major free nations. This frustration goes beyond the weaknesses and limitations of the summit process.

At a meeting of the Trilateral Commission in Rome a couple of weeks ago, which I attended as a guest, these matters were fully discussed by business leaders, bankers, academic experts and former high government officials.

The overarching fear expressed at that session is the possibility that Europe may be caught smack in the middle of a shooting war--which could be nuclear--between the United States and the Soviet Union. As former French prime minister Raymond Barre put it, Europe doesn't want to get involved in a war against Russia, with which it has coexisted for centuries. If an armed conflict should erupt, Barre added, it would take place on European territory.

When fear of nuclear escalation is expressed in the safely capitalist confines of the upper-crust Trilateral Commission, it can't be brushed off as the irrational concern of a radical "peacenik" movement.

And as will be made clear again at Williamsburg as it was last year at Versailles, European heads of state as ideologically divided as Margaret Thatcher in Great Britain and Francois Mitterrand in France also reject the idea that economic sanctions against the Soviet Union, or restrictions on the volume of trade or credit, will alter Russian policy.

Europeans agree only that high-tech exports and preferential credit arrangements for the Eastern bloc should be avoided. Beyond that, they don't want to be pressured by Washington. In short, Europe wants to do business with the Russians: they'll give up aid, but not trade. This poses a fundamental conflict with the Reagan ideology.

Turning from East-West to West- West issues, there is acknowledgment that because of economic stagnation, free trade today is a concept honored mostly in the breach. The United States presses for negotiations to hammer out rules on the trade in non-goods: services, computer information and the like.

But Europe--in this case led by France--resists American pressures to liberalize trade, preferring to stay with farm subsidies and other protectionist devices. The rhetoric supports multilateral arrangements, but politicians resort to bilateral deals.

There is, in fact, almost as much infighting and distrust among the member nations of the European Community as there is between the community and its now archrival, Japan. One highly respected think tank, the European Institute for International Relations, has just published a report warning that the Euopean economic success story of the 1950s has been "halted if not reversed." The very existence of the community, said a half- dozen authors from different nations, "is under serious threat."

Looking past Williamsburg, which seems destined to settle no big issue, there is much talk about the need for a new Bretton Woods conference to deal with the related trade, finance and Third World debt problems. But I found no serious hope that such a conference, if called, would be successful.

That sense of helplessness is the single most troubling thought I bring back from Europe. Almost everyone agrees that the need to grapple with global economic problems is even more critical than ensuring the fragile balance between American and Russian nuclear power. But no one can visualize a formula for a common approach to these massive problems, only a drift into further complexities.