Starting-up the VM of Windows 10 on my MacBook Pro takes more than 60 seconds

I'm using version 15.1.3 (47255) of Parallels desktop for Mac Home Edition and installed end of January 2020 a virtual machine based on Windows 10 64 bit.
The MacBookPro I'm using is quite power-full, with 16GB of RAM and more than 1 TB of empty space on my SSD.
Initially starting up Windows 10 was a matter of seconds, but since about 2-3 weeks it takes me more than one minute to get the desktop becoming visible and about 15sec more before I anything can do.

Is there anybody who can give me hint how to overcome this.

Thanks in advance.

Michael