He goes from not going into work one day to overtime the next! Don't understand it!

I really wish I understood how his mind works.  I thought today was going to be another day of not going to work--they are so frequent now that I don't even get upset about it with him anymore because it is too draining. He got up at 4AM and sat on the bed like he was really tired and then reset the alarm. Well that's usually the kiss of death right there because he hasn't gone in late in a year and either goes in on time or doesn't go in at all. But he surprises me and gets up at 4:30 and goes in. I figured he'd either come home early or come home at his regular time and take a nap. Nope. Just got a text for him that he's going to work a couple hours of overtime. I don't get how he can go from "I hate work and I'm not going to go in for a week" to the next day "I'm really tired but I'm working 2 hours of overtime today". Just like about 6 months ago. He stayed up all night playing video games and watching tv for no reason yet still went into work at 4AM the next day. However a few weeks later he was tossing and turning during the night and I shook him and asked if he was getting up for work and I got a very snarky "Didn't you hear me tossing and turning all night?! I only got about 2 hours worth of sleep and I am expected to be able to work on that?". Um...you worked on NO sleep a few weeks ago and acted like I was crazy when I asked if you were really going to work on no sleep! Of course you were going in...why wouldn't you!

He'll probably beat me home by about 45 minutes tonight and I'll walk thru the door and he will act SO tired and grumpy and expect me to drop at his feet because HE worked overtime and he shouldn't be expected to do ANYTHING!