2015 BMW 3 Series sudden braking feeling when driving

Mostly when it rains driving normally then suddenly it is like car suddenly loses power and feels like brake comes on , accelerating out of it but feels like it wanders to the right. 3 garages have looked at it and find no fault. Drives normally afterwards.Happens very intermittently. No specific drive speed at the time, happens at various speed.New brakes , discs suspension etc.