You're probably handling too much weight to get it right, being a beginner. I'm not saying that you are or are not strong, but that you're in the perfect place to get the technique down.
With your musculature and connective tissues, there are some prereqs for good technique.
You're hips have to be relatively loose.
Your glutes, hams, hips, back, and core should balance out your quads. Think of it as a total body exercise more than a quad exercise (depending on what style of squat you want to do).
Don't stand tall, like you're at attention. Kind of want your hips to be kind of wide, relax your glutes a little bit.
I read, and have great benefit in, a recent article by Dave Tate where he talks about the prevlance of "accordion squats", which he takes issue with. He says to "sit between your legs". The more I concentrate on this, the easier it gets to do squats, especially deep ones.
I used to pile on way too much weight and do half-squats. That's not a challenge, I have real strong quads and weak everything else. It's taken me a good while to learn how to do squats the right way.
I usually warm up with 2 or 3 sets of the bar, another set of 135, maybe another one or a set of 185. I do around 300 for 8-10, which is not great but I'm enjoying squats a lot more these days. I usually don't do real well with an extended warmup-but I found with squats I have to limber up a bit and I don't trail off in the subsequent sets.
Make sure you do good, parallel or below squats. Some good mornings also sound like a good idea for you, but definitely DON'T go crazy on the weight with these ( I would literally start with the bar and start adding dimes on each side, but read about these first if you havent already).
Your knees can travel just a bit but it really is like sitting into a chair. Find a box and a knowledgable spotter if you need more help.
bar x 5 x 2
135 x 5 x 2