Welcome to Microsoft Q&A forum and thanks for posting your query.
Could you please double check if your On Prem server meets the SHIR pre-requisites.
The recommended minimum configuration for the self-hosted integration runtime machine is a 2-GHz processor with 4 cores, 8 GB of RAM, and 80 GB of available hard drive space. For the details of system requirements
I would also recommend you to please review the SHIR - Prerequisites
Also please refer to this troubleshooting guide doc and see if that helps - Troubleshoot self-hosted integration runtime
It's really hard to predict what could be the reason for this behavior as SHIR is managed by user and many factors can cause this issue. I would recommend you to file a Support ticket so that a Support engineer can collect necessary logs from you to have deeper look and provide the exact root cause details and resolution for the issue. In case if you don't have support please let us know here.