Hi Brambles2023,
Since the Notes app on your device is running slow, we recommend that you try the steps here: If your iPhone or iPad is running slow - Apple Support
To perform the steps in the article we suggested above, click and open the link, read the subheadings below, and try each step.
1) Check your network conditions
2) Close an app that's not responding
3) Make sure you have enough storage
4) Turn off Low Power Mode
5) Keep your device from getting too hot or cold
6) Look at your battery health
The reason why we are recommending the steps above is because they will show you what to do if your iPhone or iPad is running slow.
If you’re still experiencing the same issue, the we suggest you try the steps here:If an app on your iPhone or iPad stops responding, closes unexpectedly, or won’t open - Apple Support
Please let us know the outcome after giving the above steps a try.
Thanks for using the Apple Support Communities.
Cheers!