Everyone has sleep cycles.
In babies, these last 45 minutes.
Babies can stir, or wake themselves up in between these cycles, and my squirm, or cry for a few seconds.
This is normal, and shouldn't be concerning.
Leave them alone, and observe.
The baby will self-settle, and drift back off to sleep.
This self-settling is a crucial, and important skill that all babies need to develop so that they remain calm and relaxed as the grow.
Information in this blog is from my own personal experience / observation and only for my own reference. If you find it useful, then great, buy it shouldn't be considered "gospel", and your own experience may and will differ as each baby / situation is different.