Welcome to the forums
There is an explanation why this might happen.
1.VM start after host restart:
Look on the host configuration tab - Virtual Machine Startup/Shutdown
See if this VM is selected to start when host start
Disable this if you don't want it
2. All changes on VM discarded after reboot
Right click the VM and select edit setting
Have a look at the Hard disk options, It might be set on Independent - nonpersistent
Untick independent or select persistent
Please award points by clicking correct/helpful :smileyhappy: