I started first feeling like this about 2 years ago. It started happening in gradual steps.
At first I thought maybe I just hated the gi, so I did more nogi.
Than I thought maybe I just hate going to class and just went to open mats.
Then I thought maybe I'm just going too much, so I started going less.
When you don't like someone or something, little things will start to bother you. If you enjoy someone or something, even significant obstacles will seem trivial. I found myself just making a lot of petty complaints about bjj that were indicative that I was burnt out. Meanwhile I was really going out of my way to try and learn wrestling.
The truth is I just have way more fun wrestling at this point. Sometimes wrestling sucks too but only because its hard to do, not because I've grown weary of the actual practice.
Interestingly I just got back from training. I had a great time. I enjoyed touching base with everyone. I really enjoyed helping a guy who is really starting to fall in love with bjj. The rolling was OK - not boring but not crazy fun like it used to be either.