Generic muscle pain - unless you have had some traumatic incident (like pulling a muscle) excessive muscle pain can be due to a few things. If you are starting exercise again after a long break, or beginning working out for the first time you can start feeling drained and tight/tender all over. Alternatively, it can crop up as you are progressing your training and neck deep in a macrocycle. Typically this pain can be narrowed down to A. recovery, B. nutrition and/or C. technique/loading.
It is actually very difficult to overtrain! Olympians and high level athletes (and yes you too, theoretically at least) regularly do 2-3 sessions a day, 6 days per week without overtaining. The difference is that elite level athletes will typically take ice baths and have regular naps throughout the day. They also get their 9 hours of kip every night (8 hours is a misconception - aim for 9 hours until you are about 64 years old - if you fall short, that’s life) and eat well for their sport. The issue most of us face is under-recovery, not overtraining. What does this mean? We are likely not getting the sleep or nutrients we need for recovery (i.e. 2g per kg of bodyweight if we are training), or our 9 hours (or 7 hours minimum.. kids, work, life happens - even 7 hours might be a miracle).
The final option is that we might be lifting with an incorrect technique that is overloading a certain muscle group or possibly we are enjoying the benefits of being fit but doing too many mirror muscle workouts (i.e. 10 sets a week of back exercises, i.e. pulls/rows/chins, typically also hit biceps - so those extra 10..20…30 sets of bi’s you're hitting each week is probably too much). Throw in some trap bar deadlifts or squats. Everyone knows big arms don’t count if you have chicken legs.