Hello,
This issue that theALmighty66 has -
Sudden Trackpad Malfunctions?
If the battery isn't bulging and pressing against the underside of the trackpad, it could simply be something like debris/foreign matter or even some form of liquid damage around the trackpad area as previously mentioned. In my experience, I haven't seen the issue caused by anything other than those suggestions.
Depending on your version of OS X/macOS, you can enable > System Preferences... > Accessibility > Mouse & Trackpad >
Ignore built-in trackpad when mouse or wireless trackpad is present.
See if that works for you.
C