Yup. Keep in mind the squat is an extremely taxing movement so it would make sense that it could get exhausting.
As others have mentioned, have you been getting enough sleep? I don't usually get enough sleep so I have a cup of coffee about an hour before lifting to keep my energy levels up.
What is your diet like?
The best word I can use to describe my diet is...inconsistent. I am currently working on my discipline to eat under 2000 a day to try to cut, but I generally only acomplish that every other day...
Other than that, I take protein powerder and creatine in the morning, and get over 100g of protein every day. its just that some days I have WAY too many calories (I am sure its like 3500 or 4000)
If you are looking for overall content, its not terrible. I don't do much in the way of soda, or simple sugars becuase my wife makes almost everything from scratch.
As far as sleep, I am doing the best I can, but I get 6-7 hours of sometimes interrupted sleep (I have a 7, 6, 5, and 1 year old, and my wife and I do foster care and somtimes have 1-2 others of ages 0-5).
I have generally been trying to avoid caffeine, since it tends to effect me heavily and I can't get to sleep.