That's actually intentional - to minimize the effect on Windows startup (i.e. on other programs you may want to launch or be launched early), the start of the Avast UI has been delayed - which includes the tray icon.
However, it doesn't mean that your machine is not protected till then - the main service (AvastSvc.exe) is launched earlier and it doesn't need the UI to be running to scan and block infected files. So the real time protection is running, you just don't know about it for a while.
Thanks for the explanation.
However until Avast UI is loaded, the system remains sluggish.
This issue only started since the Nitro Update.
Is there a way I can make Avast UI start without delay, I assume it won't be possible via services.msc.
You might want to open task manager as soon as you can, because you will see avastUI.exe running in task manager, much sooner that you will see the avast tray icon. That is certainly the case on this system.
Yes, you are correct. I want the tray icon to start immediately however.