Why does Bitlocker intermittently require SQL service restart after sleep?

I have a development machine that has two drives: C:\ - Operating system (Win 10 Ent) and SQL Server 2012 Standard installation D:\ - SQL Server databases, backups, logs I recently activated BitLocker on both drives, then activated auto-unlock because I realised that SQL Server can't access the databases unless the drive is unlocked. Now with SQL (and only SQL, all other services/programs are fine), on an **intermittent** basis I see the following behaviours occur: 1. After waking from sleep mode, and then starting SSMS, I cannot log in (login fails with invalid credentials error). This occurs for the Windows login account only 2. If login succeeds, or if I login using the **sa** account, then all databases are in the Pending Restore state I guess both of these are due to the drive becoming locked during sleep (or perhaps not?)? After waking from sleep, if I restart the SQL Server service, and then restart SSMS, everything works fine. I wondered what might cause this to be intermittent please, or if my assumptions are wrong, what is actually causing this? *PS. Perhaps a BitLocker tag might be useful, as I see there are plenty of other questions relating to this???*