Crying in sleep

Anyone else’s baby break out crying while fast asleep? Mine will start wailing like 30-45 minutes into a nap and still be fast asleep while doing it. Sometimes she will quiet back down and fall back asleep and other times she will wake herself up. I really think its due to her sleep cycle changing, but it’s the saddest thing to witness. Anyone else going through the same? Anyone know when she will outgrow this?