Plunging from crisis to crisis, the United Mine Workers Union has now become trapped in a Catch 22 of the coalfields: wildcat strikes to protest medical benefit cutbacks that are caused largely by wildcat strikes.

A series of unauthorized strikes, called for a variety of reasons over the futile protests of union leaders, had cost the union's health and retirement funds an estimated $65 million - or more - since 1974.

The loss stems from the fact that the funds are financed by industry contributions pegged to the amount of coal that is mined and the number of hours that are worked.

In announcing cutbacks that could cost miners' families up to $500 a year, the funds' trustees said last Monday that the action was necessary to avert a cash-flow deficit of $26.2 million in medical benenfit funds by December.

The action immediately triggered a new wave of wildcat strikes. As of Friday, an estimated 31,000 workers - one-sixth of the union's working miners - were off the job in protest.

This was the last day before the start of miner's annual two-week vacation, which union leaders hope will serve as a cooling-off period.

If it doesn't and the work stoppages persist after the vacations taper off in mid-July, even more severe cutbacks may be required, such as suspension of the free drugs program, according to the trustees.

Arnold Miller, who was recently re-elected UMW President on a claim that "the best is yet to come," decried the cutback and blamed it on th coal operators. But Miller, who faces post-election challenges from at least one of his two rivals for the presidency, has conceded that he can't control the wildcats.

Many observers are predicting that, even without more cutbacks, the disension-wracked union will wobble toward its Dec. 6 contract renegotiation deadline in an unhappy mood and fitful work pattern, virtually guaranteeing a nationwide coal strike before the end of the year.

As many as 100,000 miners were out of work during the peak wildcat season late summer, and about 30,000 were out last month in a dispute over absenteeism rules. Time lost in work stoppages thus far this year has nearly doubled from the same period last year.

The funds' trustees - who include representatives of both labor and management but are independent of both - estimate that the strikes have cost the funds $65 million since the 1974 contract was signed. The Bituminous Coal Operators Association, the industry's bargaining group, estimates the loss at more than $81 million, including $18 million in the first five months of this year.

Twice before over the past 13 months the funds' trustees, with the agreement of labor and management bargainers, reallocated royalties among the union's four separate trust funds to avoid cash-flow deficits in one or more of the individual funds.

This time the trustees ordered sharp reductions in medical benefits as of July 1. These "cost-sharing measures," as the trustees called them, would require the 821,000 UMW beneficiaries and their families to pay the first $250 of any hospital bill and 40 per cent of doctor bills, up to a combined total of $500 per year. Previously all such bills were paid by the funds.

Miller blamed the situation on industry "callousness," asserting that the BCOA should have sought a reallocation of royalties (as the industry contributions are called) from one of the pension funds.

BCOA President Joseph P. Brennan retorted that a reallocation would "subsidize and condone wildcat strikes" and make it difficult to meet new legal requirements for advance funding of pension plans.

Of the four funds, the health fund that serves active miners is in the worst trouble, losing $4 million to $5 million a month, according to th funds' officials. But the pension fund serving this group takes in much more than it gives out, and, according to Miller, has $300 million in invested assets.

The question is whether royalties can continue to be transferred from this pension fund without violating the requirements for annual pension contributions under the 1974 Employee Retirement Investment Security Act (ERISA). Miller says they can, Brennan says they can't, and it takes agreement between the two to get a reallocation from the trustees.

The issue is clearly headed for the bargaining table this fall and could be as serious a problem as the union's demand for a right to strike over local grievances, previously viewed as the stickiest issue.

"Every single additional dollar that coal miners are forced to spend for health services will be returned to them - with interest - before a settlement is reached this year," Miller vowed in his statement attacking coal operators.

Brennan's refusal to countenance any action that "condones" wildcat strikes presages a tough bargaining stand by the industry on the benefits pay-back issue.

As if his troubles weren't bad enough already. Miller has been accused by one of his election challengers, Harry Patrick, of deliberately withholding the trustees' decision until after the June, 14 election. Both Patrick and Lee Roy Patterson, who ran second behind Miller, predicted the cutbacks during the campaign.

Patterson and Patrick each contend they were wronged in different ways and Patterson has said he will challenge the election before the union's largely anti-miller executive board.

A possible scenario for Catch 23: a union trying to prepare for contract bargaining while its leaders are campaigning for re-election, its members are out on unauthorized strikes and its benefit funds are drying up.