Autoclose is on for those databases. So whenever no one's using the DB, SQL shuts it down. When you need it again, SQL starts it up and recovers it (going through recovery)
Maybe also log fragmentation (excessive VLFs)
Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
SQL In The Wild: Discussions on DB performance with occasional diversions into recoverability