The UDP 137 packets from your Win95 machine is the machine announcing
itself to the network in an attempt to determine who is the NetBIOS Browse
Master for that network. In the event it cannot find one, it will become
the Browse Master itself. I would suspect that your packets came about
simultaneous to reboots or power-ups, which you could confirm by monitoring
a power-up sequence and seeing how many packets it generates.
You can turn off this capability, thereby forcing it not to attempt to
become a Browse Master by going to Control Panel, Networks, File and
Printer Sharing for Microsoft Networks, Properties, Browse Master = No.
Make sure you have applied Service Pack #1 for Windows 95 to an Internet
exposed Windows 95 machine that has File and Print Sharing enabled.