Do you mean twice in one year? Not usually but it can happen.

My magnolia is carrying a few flowers again. It often happens in a warm summer.

Mine has flowered twice in one year but not as many the second time round.

Magnolia grandiflora could easily, depending on how warm and long the season is. Much less likely in the deciduous species.

Yes it's normal for a magnolia to put out subsequent blooms after the main flush.