Like others are saying, probably a clogged nozzle. However, I want to say I just went through this myself and it was not a clogged nozzle. At temperature, I could put light pressure on the filament with my hand and it would come out smoothly, no clog. It can also be that your nozzle is too close to the print bed. In my case, it would do this even when suspended in the air, so that was not the issue.

I upgraded to a metal extruder, and no longer have this issue.

Despite what everyone says, sometimes parts are the problem.