Those look much like Bonjour / mDNS requests to me. Those packets use multicast IP address 224.0.0.251 and port 5353.
The most likely source for this is Apple iTunes, which comes pre-installed on Mac computers (and is a popular install on Windows machines as well). Apple iTunes uses it to discover other iTunes-compatible devices in the same WiFi network.
mDNS is also used (primarily by Apple’s Mac and iOS devices) to discover mDNS-compatible devices such as printers on the same network.
If this is a Linux box instead, it’s probably the Avahi daemon then. Avahi is ZeroConf/Bonjour compatible and installed by default, but if you don’t use DNS-SD or mDNS, it can be disabled.