Shutdown other running notebooks.
1.1 Go to the Jupyter Notebook Home Page by clicking the File List icon in the upper left corner.
1.2 Click the Running Tab.
1.3 Shutdown all running notebooks.
1.4 Return to your current notebook and restart its kernel by pressing 0 0.
See if you can reduce the size of your datasets that are loaded into memory.
If the issue persists, you will probably have to choose either SMALL or MEDIUM memory when starting your session.