This is a common problem & it could be due either to the mouse or the touchpad. First, as AMIS says, the mouse could need a clean, especially if it's a ball mouse. If it's an optical one with a light underneath, it could be that it doesn't like the surface it's on - a strong pattern can throw a lot of mice - they seem to have a particular dislike for woodgrain with a strong contrast.
Or it coild be the touchpad - some keyboards are very 'bouncy', especially if you're a fast or energetic typist and can affect the toyuchpad. Or possibly your sleeve/edge of your hand is brushing the touchpad. If you don't use the touchpad much, you could turn it off. Some computers are just prone to this - several models of Acers especially the 5315 & 5720 are particularly bad, it can help to turn off the 'tap to click' function: Control Panel-Mouse-Properties-righthand tab & look for buttons/sliders to do with tapping (it's different for various computers so I can't be more specific.) Mine actually has a slider to change the sensitivity to guard against accidental touches - have a look & see what you can find!