Trackpad going bad?

That problem is often caused by battery failure that manifests in it becoming swollen and exerting pressure on the trackpad from beneath. Have that Mac evaluated by Apple at your earliest convenience: Start a repair request

Or it could just be dirt, crumbs, and/or liquid residue blocking the motion of the Trackpad on 2015 and earlier laptops. Or it may indicate the Trackpad switch is failing. The majority of the time it is either dirt/liquid or a swollen battery as suggested by @John Galt.