Q: Built in trackpad not functioning

Hi,

My built-in trackpad appears not functioning well. The cursor seems to have a mind of its own- it's movements are erratic. I have done SMC and PRAM reset though there is no change. I have unchecked all the options on the Trackpad settings with no resolve. I also upgraded the OS to El Capitan yesterday

I have a MacBook Air 13" mid 2012. OS X El Capitan 10.11.4.

KIndly advise on how I resolve this issue. Thanks in advance.