delay at the beggining of opening or downloading file via samba/afp

When I want to open a movie (or just copy big file from nas), no matter if it's over samba or netatalk - process starts after 20-30 seconds.
General connection is fine, because when I type command to download file over scp - it starts immediately.

Do you guys have any idea what I could check..? This problem is super annoying

huh - it was antivirus. Weird, since before this problem appeared, I was using nas with antivirus for last year.. but anyway, topic solved.