The multi-touch trackpad’s on your MacBook should have a substantial click sound to it, and require a notable press to activate. Granted many people will have differing touches, but in general you should be able to swipe around on your trackpad without activating the button on it. If this is not the case and your trackpad’s button does click inadvertently and quite frequently, then there may be some quick fixes you can try.
First of all, ensure you do not have tap-to-click enabled unless you specifically want it. While this is convenient for some people, it can turn the slightest graze of your trackpad into a click that activates some function of some program or system service you did not intend. Unless you have tap-to-click enabled, then this is likely a physical issue with your Mac, as opposed to a software bug. Therefore, restarting your Mac, or using Safe Mode, or even reinstalling your Mac should not affect it, and the methods for fixing it may require you go hands-on with your Mac:
Click rapidly
While the trackpad has only a fraction of a millimeter between it and the surrounding case of your MacBook, this can be enough to lodge fine hairs and other debris. If this collects, it can interfere with the movement of your trackpad. Therefore, try clearing it out by using canned air in combination with rapidly clicking your trackpad. This is no guarantee to fix the block, but in some cases it can help wriggle out recently collected debris that could be causing the issue. The trackpad hinges around the top, so when doing this, concentrate your efforts toward the bottom edge of the trackpad.
Slightly pressure-bend the chassis
Apple’s MacBook systems are engineered with fine tolerances between components, and in this case your trackpad might be resting slightly lower in its housing, or be otherwise slightly occluded from the bottom. To provide a little more relief, with your MacBook open, grab the left and right sides of your Mac’s palm rests, and place your thumbs on either side of the trackpad. Then press with your thumbs and pull up with your fingers to gently bend the system very slightly. This will not warp your system at all, but will help re-seat components like the trackpad and battery which may be pushing against each other.
Check your battery
One possible reason for trackpad occlusion is if your battery is damaged and is swelling, which may have it pressing against your trackpad and warping the system slightly in the opposite direction of the pressure-bend steps above. This will cause the button to be pushed up into the trackpad, and require far less of a click (if any) to activate. You can usually see this by opening the bottom of your system and seeing if any of your battery packs show protrusions or bulges. For guides on how to open your system, check out iFixIt’s Mac Laptop Repair section.
Service, if necessary
Finally, if you cannot seem to fix the problem, or see that it is from a battery fault, then take your Mac in for servicing.