Apache 2.4 long delay before first response

I've test server (Centos 7) in my local network with Apache 2.4. All works fine, but each time after about 1 hour of inactivity Apache responding with a lag about 4.8 sec. Next requests proccesed very fast (1-5 ms).

The lag appears AFTER connection (connect – 1ms, request sent – 1ms, waiting TTFB – 4.8s). The problem occurs regardless type of requested source (html page, html +php or just image). Another network applications works w/o lags.

IPv6 disabled. IP and port configured in httpd.conf:

ServerRoot "/etc/httpd"
Listen 192.168.0.100:80

KeepAlive On
MaxKeepAliveRequests 0
KeepAliveTimeout 300
Include conf.modules.d/*.conf

User apache
Group apache

ServerAdmin root@localhost
ServerName 192.168.0.100:80

<Directory />
    Options Indexes FollowSymLinks
    AllowOverride all
    Require all granted
</Directory>

DocumentRoot "/Site"

<Directory "/Site/www">
    AllowOverride None
    # Allow open access:
    Require all granted
</Directory>

<Directory "/Site/www">
    Options Indexes FollowSymLinks
    AllowOverride None
    Require all granted
</Directory>

<IfModule dir_module>
    DirectoryIndex index.html
</IfModule>

<Files ".ht*">
    Require all denied
</Files>

ErrorLog "logs/error_log"
LogLevel warn

<IfModule log_config_module>
    LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\"" combined
    LogFormat "%h %l %u %t \"%r\" %>s %b" common

    <IfModule logio_module>
      LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-Agent}i\" %I %O" combinedio
    </IfModule>
    CustomLog "logs/access_log" combined
</IfModule>

<IfModule alias_module>
    ScriptAlias /cgi-bin/ "/Site/cgi-bin/"
</IfModule>

<Directory "/Site/cgi-bin">
    AllowOverride None
    Options None
    Require all granted
</Directory>

<IfModule mime_module>
    TypesConfig /etc/mime.types

    AddType application/x-compress .Z
    AddType application/x-gzip .gz .tgz

    AddType text/html .shtml
    AddOutputFilter INCLUDES .shtml
</IfModule>

AddDefaultCharset UTF-8

<IfModule mime_magic_module>
    MIMEMagicFile conf/magic
</IfModule>


EnableSendfile on
IncludeOptional conf.d/*.conf