Only normal breathing while lying flat on back?

Depends on details: Question is vague. Breathing is something people can do in almost any position. If a woman in her 60's has somewhat sudden, new onset breathing problems, that is reason enough to call 911 for a trip to the ER to get checked out. If symptoms are very, very mild, and she has no history or heart or lung disease, maybe she can talk with her primary care doctor now, to ask about ER vs. office visit.