Hangfire 1.6.3 application pool recycle leads to CPU spike

This morning the app pool in our hangfire application in our server got recycled. That seemed to trigger the CPU spike (100%) for about 15 minutes.
We also encountered SQL time out error during that period.

But after 15 minutes the CPU went back down to normal and the SQL error is also gone.

Connection Timeout Expired. The timeout period elapsed during the post-login phase. The connection could have timed out while waiting for server to complete the login process and respond; Or it could have timed out while attempting to create multiple active connections. The duration spent while attempting to connect to this server was - [Pre-Login] initialization=0; handshake=5109; [Login] initialization=0; authentication=0; [Post-Login] complete=24009;

Our app pool is recycling every 1740 minutes and the CPU didn’t spike always but it did happen on some occasion.

Do you have any explanation on such behaviour?
Any advise is very much appreciated.