Looks good. You would probably feel better with a slightly wider stance. Also, you don't have to squat so low. Cut it off by a couple inches and you'll find a stronger stretch reflex at the bottom. Notice how your back angle suddenly becomes more vertical at the bottom as your hips drop down (without the bar moving lower), it's not necessary. Yes it's pretty common for warmups to feel heavy and the first work set to feel heavy. For me the 2nd work set almost always feels the best.