This is common and all I can tell you is it will pass, I have started low carb diets 3 times in the past (I stopped them after the weight was off to my demise each time, not this time though). I will suggest you open up your diary so people can input or invite me as a friend so I can look through and see if you are balanced on your intakes. You are likely just getting to ketosis and your body is trying to get the energy stored in your fat cell.

What are your macro goals?

Yeah, the first 2-3 weeks (sometimes 4 weeks for some) of starting low carb sucks! I think we've all been there. The body wants the carbs it's use to burning and is upset it's not getting them. So it needs to remember how to burn fat again. It takes a while, but you'll have lots of energy once your body remembers.

In the meantime, make sure you're eating plenty of calories. I didn't even cut calories, until my body was use to low carb. I agree with Miamiuu and kiramaniac. Have some caffeine in the morning like coffee with heavy cream or a diet drink to help get ya going. Make sure you're getting enough dietary sodium, potassium and the forgotten vitamin K. You can get a lot of potassium and vitamin K from eating leafy green veggies. Kale is a really good example. Increasing my leafy green consumption really helped me get over the hump. And of course drink enough fluids. :-)

Keep at it. You'll get there!

I was stuggling with this a bit too. I'm midway through week 2. For me its not lack of sodium, I add sea salt to most foods and don't restrict my sodium at all. I've found that adding vitamin D has helped me a lot.

My guess:
You're not eating enough calories consistently. I'm so guilty of this often. Based on your profile, your current BMR is about 1306 and TDEE is about 1567 without exercise. Try to eat in between your BMR and your TDEE daily. If you begin exercising regularly, even light exercise, your TDEE will be much higher. You'll need to eat even more.

I don't know what your fiber count is, but it's very important to get enough fiber in your diet while low carbing. Women should be getting about 25g daily, men 30g daily. If you've been eating under 20g of carbs for the last 8 weeks, you should bump up your carbs. You're glycogen stores have likely already been depleted and you're burning fat now. This will help with getting more fiber into your diet too.

If you can, try taking a 10-15 min break at work and go for a leisurely walk, even inside around your building. I feel like I have less energy when I get home from my desk job if I haven't had a walk or two at work. Having a small snack if you need a boost of energy before you work out may help. And, eating more leafy green veggies will help too such as kale, leaf lettuce (not iceberg), spinach, etc. Being dehydrated can make you feel tired, make sure you're drinking enough non-caffeinated liquids. Then general rule is 1/2 oz for every pound you weigh. As for sodium, it should be a little higher. I feel good around 2500-3000mg daily, but your needs may be different.

Also, unless you're buying enteric coated or slow dissolving multivitamins, it's likely not helping much. Most cheaper multivitamins are rendered ineffective/destroyed by stomach acid. I believe the only vitamins not destroyed in stomach acid are B and C vitamins. The last stat I read was 7-11% of a multivitamin is absorbed by the body, so not a whole lot. You can improve the absorption rate by taking it when you eat a meal, but not by much. If your eating a well balanced low carb diet full of lean protein, healthy fats, veggies, nuts, berries, etc., there really is no need for a multivitamin, assuming there isn't an underlying medical condition. Enteric coated vitamin absorption rates are around 60-80% last I read, at a cost of $50-$60+ per 100 to 120 tablets. Not really worth it IMO. Save your money.

Hope one these suggestions works for you! Keep truckin'; keep trying. You'll eventually figure out what works for your body. Good luck!