Every artist in every genre experiences this from time to time. I have some solutions which have always worked for me.
1: Get out and get inspiration... you increase your frustration by sitting there, and the tension is subconsciously de-motivating you. The fear of a blank canvas is very real. Deal with it by taking a walk, if possible take a tour of a fine art gallery and just enjoy the paintings, and your enthusiasm will likely return before you're half way round the exhibits!
2. Paint your canvas randomly. This depends on how you've primed it already. I sometimes pick a tube of paint randomly, mix it into a wash, then apply it very energetically to cover up the white canvas. When that's dry, I try to interpret the faint shapes caused by my brush strokes, and make some kind of a painting using them as guidelines.
3. Set yourself to render in paint an emotional experience. A dream. A fantasy. Something that pleased you as a kid. I once even picked up an encyclopedia, and stuck a pin in randomly... I landed on the word gall bladder, but that developed into a painting of a hospital!
4. In my humble experience (but I have sold a few canvases, so I think it counts!) the internet is NOT a good source of inspiration. The images on the screens are flat (even 3D TV is made of layers) and it atrophises your artistic vision, as well as having proven links to depression (which might prevent you being motivated to paint). With the help of the internet, you can procrastinate indefinitely, and also completely lose your creative drive, so get out and experience the real world.
5. Your painting mind might be fatigued (this is true of writers block also) with running in the same channel. Live a little, try mixed media, maybe go to your art store and look at other media which you have never tried before, maybe oil pastels, mosaic and other craft materials. Don't fall into the trap which I often got caught in... that of being too snobby to experiment with "craft" materials rather than "fine art". Most materials offered now are of high quality and durability, unless you get your supplies from the dollar store.