Trackpad Issues

Hi Everyone,

After scouring the internet for ages I have finally decided too see if I can get any help here (thanks in advance)!

I am having a deeply annoying issue with the built-in trackpad on my MacBook Pro 11,3. After booting, the trackpad will work perfectly for about 3 seconds and then whatever I do on the trackpad (apart from clicking, strangely) will happen about 15 seconds later (so every action on the trackpad is delayed by around 15 seconds). On top of this, the trackpad occasionally clicks on random things on my screen, zooms in and out on webpages, moves my cursor and randomly highlights text (although, this is quite rare). I have tried pretty much every solution under the sun (SMC reset, PRAM/NVRAM reset, Apple Diagnostic tool, re-installing MacOS, deleting .plist flies, completely erasing the hard drive and reinstalling MacOS, scanning my computer for viruses) and nothing has worked. I would be super appreciative of any help anyone has to offer! (I am currently using a USB mouse which is a bit of a nuisance and sort of defeats the purpose of a MacBook. Also, the keyboard is unaffected.)

Again, thanks soooo much in advance!