New to 3d printing, my ender 3 is having problems with thermal runaway and doesn't seem to be able to keep a consistent temperature when I begin printing.

It however does not have issues maintaining the temperature when it's not actually printing. I can set my hotend to 215 before beggining my print and it's happy to sit there.

Other problems with it include under extrusion and extruder skipping, as it seems to have troubles pushing the filament out.

What does this sound like it could be? Does it sound like a blockage? Could a blockage cause temperature issues? I have already tried turning off the part cooling fan as I had a similar issue with that a while back but that has no made a difference it seems.