Issue
You have multiple jobs sitting in Runnable state, and they are stuck Waiting for workspace, and that workspace has some issue (file permissions, NFS mount issue), so those jobs keep retrying to run (this is expected behaviour).
If there are other jobs that are not waiting on that workspace with an issue, they can sometimes never get scheduled, since the job scheduler is re-trying to schedule these jobs which are waiting on a workspace and previously failed to become scheduled.
Here is what it looks like when your job that is waiting on a workspace that has an issue (in this case, the permissions prevent the workspace directory from being created):
Resolution
If you have a workspace that is not accessible (due to directory permissions or a bad NFS mount), you may see multiple jobs in this 'Waiting for workspace' state.
To figure out which directory has the issue, and what the error is, click on the Job Step Details in the GIF above, to see the exact directory path with the issue, and fix the permissions, or correct the NFS mount issue.