My main focus of working out is cardio, since I want to lose weight. I do 60 minutes of cardio 3-4 times per week. I do a very minimal amount of weight training--3 sets of 20 leg presses, 3 sets of 15 leg extensions, and 3 sets of inner/outer thigh movements. It all takes about 10 minutes. However, I am always very sore afterwards, and am therefore not motivated to exercise at all. I think it's largely due to the leg press (although I'm only doing 30 pounds on it). I know I'm using all the machines correctly. I am still fairly new to this routine, so is this normal? A couple of days after my first day of weight training, I get so sore that I can't walk normally.

Yes, soreness is very common for someone new to weight training. It's basically caused by your muscles ripping and rebuilding themselves in response to the stress you gave them in the gym, so that next time you workout they're more capable of managing the load.

The good news is that this muscle soreness usually only occurs during the first few weeks of weight training. I rarely get sore anymore, and I've been training for 18+ months.

Make sure you're allowing plenty of time for muscle recovery between your workouts - ideally 3 days between doing the same exercises, as this allows your muscles to repair. Working out too often can actually impair your progress. You can do cardio every session though.

ya ive noticed the same thing, after ive worked out my muscles get sore, but as well as between my shoulder and neck i get like a pinched nerve, and my wrist tend to hurt alot when i lift heavy amounts to the point were any pressure on my wrist hurts. perhaps im doing something wrong? and or trying to lift to much to fast?

Yeah, you could be doing too much too soon. What people forget is that muscles grow quicker than tendons, so if you up the weight too quickly you will increase the risk of strained/ripped tendons.

Your wrist pain sounds like either you're not using proper form (somehow putting too much pressure on the wrists), or you simply don't have the wrist strength to cope with the weights your doing. In the short term you can work around this by using wrist supports, but for long term you want to do some wrist exercises too - like using light dumbbells and doing wrist curls. Eventually the strength in your wrists will improve.