European films help liven the summer doldrums.

Is it the weather? Little has been trickling from Hollywood lately but 3-D novelties and teen-age sex comedies. It's been a flimsy season so far, though things should pick up when the studios begin their fall sweepstakes, a period usually marked by more serious doings.

Fortunately, warm temperatures haven't stopped Europe from sending some real movies to American screens. One of the strongest is Ways in the Night, made in West Germany by Polish director Krzysztof Zanussi, who reached the realm of sublimity in ''The Constant Factor'' not long ago.

His new film focuses on an unusual confrontation. In occupied Poland during World War II, a young Nazi soldier gets a crush on the dowager in whose home he's garrisoned.

He is a cultured and gentle man, hoping he's on the right side in this war he'd rather have nothing to do with. And he can't understand why the woman he admires should loath him so, despite their shared European heritage and love of the arts.

The answer, of course, is her Polish nationalism - not the freshest motivation for a movie character, but emotionally moving in its fierce contrast with Nazi imperialism. The soldier moons about and quotes great books, acting like anything but a Nazi, vainly hoping for some sign of affection. She hammers out Chopin preludes and tells him to go back where he came from.

Meanwhile, subplots ripple below the surface: a scheme by the resistance movement; the capture of a hapless Jew; a continuing dialogue between the soldier and his superior officer, a brainy brute who used to be his philosophy professor and is now very Nazilike indeed.

Falling short of ''The Constant Factor,'' but soaring above ''A Woman's Decision,'' this film is closer to such middling Zanussi offerings as ''Camouflage'' and ''Kontract'' in emotional and intellectual impact. Yet it becomes very affecting when it dwells on the soldier's confused effort to understand why his background of art and culture won't stand him in good stead with anyone - not his loved one, his officer, or even the local teacher who slyly mocks his pretensions.

Zanussi avoids easy answers and cheap resolutions, deepening the movie's resonance without simplifying its implications. It's a committed and thoughtful picture, though not a brilliant one.

French comedy

If this sounds a bit heavy, summertime viewers can cool off with Pauline at the Beach, the third installment in the six-part ''Comedies and Proverbs'' series by French filmmaker Eric Rohmer.

Though the rating is R, reflecting a few moments of nudity and sexual play, it's really a ''moral tale'' like other Rohmer films, following basically decent people through a small thicket of worldly temptation and out to safety - for the moment, at least - on the other side.

Pauline, just 14 years old, is on holiday with her recently divorced cousin. Into their lives come two young men. One is a restless type who can't settle down for more than a day; the other is an idealist who craves commitment. Both court Pauline's cousin, while the teen-ager tries to figure out why adults are so cagey and conniving about something as simple as affection.

The story pivots on a single incident that could have been lifted from a Feydeau farce. But though the mood is often comic, the emotions are real, and the characters feel them deeply. By the last scene, lessons have been learned and feelings have had a workout - and it's likely no one will be quite the same after this unexpectedly complicated vacation.

In time-tested Rohmer fashion, ''Pauline at the Beach'' examines its characters in ordinary situations, then tests them by posing small (and telling) ethical challenges. Typically, they turn out to be good folks, though hardly free of foibles and shortcomings.

Also typically, the movie avoids a judgmental air by stressing its goodwill toward everyone in sight. Like a parent, Rohmer adores his children despite their flaws. He dwells so fondly on their earnestness and vitality, in fact, that these qualities become refreshing mainstays of the film itself.

''Pauline at the Beach'' has been impeccably photographed by Nestor Almendros , and it is performed with great conviction - and just the right edge of eccentricity - by a talented cast. While it lacks the weight of ''Le Beau Mariage,'' the previous entry in the current Rohmer series, it's full of the listenable chatter that has become the trademark of this heroically literate filmmaker.

Indeed, it gets too talky at times, but we know Rohmer won't let things get out of hand. He's the one, after all, who chose the picture's 12th-century epigram: ''A wagging tongue bites itself.''

The Hitchcock effect

Another current import reflects the French fascination with American-style thrillers. Even the title of ''I Married a Shadow'' sounds like a B melodrama from the '40s, and the beginning carries more then a hint of ''Strangers on a Train.''

Indeed, the spirit of Alfred Hitchcock hovers over its whole mixture of romance, deception, and eventual violence, though director Robin Davis rarely reaches Hitchcockian heights of filmmaking. He misses the master's important distinction between suspense and mere surprise, for example, by springing things on us with an abruptness that lessens their impact.

Nathalie Baye, perhaps the most appealing of today's younger French stars, plays an unwed mother-to-be with a churlish boyfriend and no prospects for happiness. On a train trip she meets the kind of woman she would like to be: equally pregnant, but married to a considerate man and cushioned by plenty of money.

In a sudden accident - the plotty kind that only happens in movies - this other woman is killed, and our heroine is mistaken for her by almost everyone. If she wants to, she can stay in the other's place - living comfortably with her wealthy parents - and nobody will mind. But this means pretending to be someone she's not. All goes well for a while, until murky warnings start coming her way, and her past threatens to return and engulf her.

Yes, it's contrived. Yet it's kind of fun to watch as the talented Baye wrestles with all sorts of conflicting emotions and copes with outlandish hitches that keep cropping up. And I, for one, can't resist pictures where the heroine's morning mail includes ominously scrawled notes saying ''Who are you?'' and ''What do you want?''

True, director Davis was in far better form in his ingenious ''Cher Victor'' a few years ago. But his mildly suspenseful ''Shadow'' will do in a pinch, at least until the weather changes.