Hangs on Shutdown

PC running Windows 98 SE hangs every time I go to shut down on the windows is now shutting down screen. Pentium II 200Mhz Processor, soundblaster sound card,96 meg ram, 3com 10/1003C905 nic card, 56k modem,HPdeskjet 600 are the only cards and devices in the machine. Running Office 2000… Machine will also auto-reboot now and then similar to a soft reboot or rest.. Any ideas?