extremely slow startup time for JupyterLab Spaces

### Product Version

- [ ] Amazon SageMaker Studio Classic
- [X] Amazon SageMaker Studio
- [ ] Issue is not related to SageMaker Studio

### Issue Description

When I launch JupyterLab Spaces, it takes 20-30 minutes to start up. The message "Loading…The loading screen is taking a long time. Would you like to clear the workspace or keep waiting?" comes up 5-10 times, regardless of whether I choose "Keep Waiting"or "Clear Workspace". This has been reported elsewhere, e.g. https://www.reddit.com/r/aws/comments/t9f9sj/sagemaker_studio_takes_a_loooonnnng_time_to_start/

### Expected Behavior

The Spaces should load in less than 1 minute

### Observed Behavior

The Spaces load in no less than 20 minutes

### Product Category

JupyterLab

### Feedback Category

Startup Time and Latency

### Other Details

_No response_

No source files, tests, or entry points are named. Start by reproducing the JupyterLab Spaces launch in Amazon SageMaker Studio and review the repeated loading-screen behavior described here. Done means Spaces consistently load in less than one minute instead of taking 20–30 minutes.

Written by the indexing model from the issue text.