Solved:- A new update for Dell Update windows universal application was available on Dell support site which I downloaded (the version which I updated it <here> ) and run that exe which failed when ran for first time then again ran it.It updated successful then I read the app description that it was told to reboot the system after 5 minutes of update.I waited 10 mins then restarted my laptop.Boom again the scan is running successfully after restart.No errors.One request to Dell engineers that please show user a notification or prompt to restart after 5 minutes.Before this error appeared i haven't waited for 5 minutes to restart so this problem happened in my laptop but now it is solved completely.
I have Dell G3 3500. The warranty expired December 2021. Windows 10 21H2 latest with all drivers updated. Today when I scan for drivers update it showed me to updates 1.BIOS update and 2. Dell update application.I updated Dell update application only and it prompted for a restart so I did restart then to update BIOS i did scan for update button again and it showed an error occur that "A task is currently running in progress.Wait for previous task to finish".The error is attached in the image.I did a uninstall supportassist then directly reinstalled supportassist.I didn't did a restart after uninstalling supportassist and after reinstallation in did a multiple restart but same error.Please help me to solve this error as I need to update in future.This happed only after updating Dell update application. Please help me to solve this.  
Supportassist scan for drivers update error