Erratic mouse behavior

Toshiba Satellite Pro 425CDC, 40M Ram, Win 95a. Mouse pointer will suddenly and randomly take off and dart horizontally or vertically to edge of screen…sporadically moving by itself. Settings for pointing device in BIOS are set to Simultaneous, the latest Toshiba mouse driver is loaded, the auto-scroll feature is disabled. Any ideas as to why this problem continures to haunt the laptop?
Thanks.