Why am I so sore after lifting?

Usually you adapt - the more frequently you lift (within reason) and the longer you do it, the less sore you should get.

If you are finding soreness other than general DOMS, you may want to look to do some mobility work for those areas.

DOM DOM DOMS! I love Doms! DOM DOM DOMS! We love Doms! DO-DO-DO-DOMS! One day, You will love DOMS too! DOM DOM DOMS!

Yep DOMS is normal and is particularly bad when you're just starting out, you add in something new or you increase volume or load significantly. Yes, it's also quite normal for DOMS to peak in terms of soreness 2 days after lifting (it can go on for up to 4-5 days).

Once you adjust to your routine it'll get better. Frequency and consistency of workouts can help (i.e. if I squat once a week - guaranteed soreness but if I do it three times a week it's not so bad). Unfortunately some people have poor genetics for recovery and seem to get worse DOMS (including me). Others are lucky and won't get it at unless they have a significant change in routine.

Things you can try include mobility work, ibruprofen, heat, epsom salt baths, foam rolling, massage, ice baths, contrast showers, slowly increasing load and volume etc. Although the literature seems to indicate that there is nothing that will actually alleviate DOMS completely these things may help a little

When I first started out I could barely move for 2 days after a work out, and actually the one thing that helped was doing other exercise. As in, my arms and shoulders were killing me, but I put on an ab workout video from youtube and completing that warmed everything up and stretched it out without putting direct load on my already sore upper body muscles. Obviously you don't want to overdo anything, but if you're just a bit sore and feel up to it this really helped me!

You are just over training and/or not resting enough, cut back.

It's absolutely normal. And after you're at it for a while, you'll realize that:

a) you get less sore because your body is getting better at absorbing work
b) you're equally sore BUT you can still put a quality workout
c) you're so sore you can't work out effectively - you need extra recovery via time, nutrition, massage, or a combination.

See "delayed onset muscle soreness". There's a lot of material online.

PS - there's a difference between hurting and being injured. Learn that as well!

The odd thing about soreness after workouts (if it is not from an injury or doing an exercise incorrectly) is that people experience it after different exertion levels and to different extents. Some almost never get any soreness, and some, like me, get soreness very frequently, almost after every workout unless I'm going light. People will claim it means this or that, but if its just post workout soreness, you are going to have to learn your own body's patterns and adjust. I find for me if I exercise hard, I cannot do entire body 3x/wk because of the soreness, this is one of the reasons I do split workouts. Any change in weight or type of exercises increases the probability and length of soreness in hours/days afterwards. Some muscles are much more vulnerable to inducing soreness when exercised heavily than others...and not always based on how often you use them. I've also noticed the initial onset of soreness has increased in time as I got older, and the length of soreness seems to have increased a bit too.

All the myths about having to stretch vigorously beforehand, getting sore only without enough protein or without certain supplements are not true. Soreness = you overdid it is not necessarily true...but can be. That last one is hard to judge sometimes at first, but you learn with time.

Either way, the things you can do that I have found moderate and reduce soreness are increasing regular sleep, and stretching after exercise, activating/exercising the muscles lightly while sore, and massage before onset of soreness.