There are about a million reasons you could be tossing and turning and/or having nightmares. If it’s really bugging you, you’re tired all the time, it’s proabaly a good idea to work on finding out why, though it could take months to get it figured out.
My experience has been that if I have vivid unpleasant dreams that I remember - which you say you’re not doing - there’s some problem in my waking life that is causing strong feelings; the images in my dreams may or may not match up with the crummy situation in real life, but the feelings do. For instance, if I’m feeling like something in my daily life is out of control and frustrating, I’ll usually have a dream about being back in high school and unable to get my damn locker open. Now that I know this about myself, if I have a dream like that, I know I have to take the time to deal with whatever it is, and that helps the sleeping.
My husband always has nightmares after eating anything with meat or fat in it within a couple of hours of bedtime. He also has really epic nightmares when he’s let his anxiety disorder get out of hand. When he’s taking care of himself, either with anti-anxiety medications or with yoga or whatever, the nightmares taper off.
On the other hand, I also have nasty dreams that sort of “explain” something unpleasant going on at that actual time - for instance, if I’m getting a migraine while I’m still asleep, I start having dreams about being shot in the head, or having my head run over by a bus; if I have to pee, I have dreams about filthy bathrooms with overflowing toilets full or crap that keep me from relieving myself; if my nose is stuffed up and I’ve been breathing through my mouth until my tongue is completely dry, I dream about eating something that turns out to be glass, or sand, or coffee grounds, or whatever. So if I were you I’d investigate to make sure nothing in your bedroom is disturbing your sleep enough to make nightmares but not enough to wake you up.
If you’re not really sure you’re having nightmares but are just a very restless sleeper, I’d make a visit to the GP if you can afford it - there are lots of conditions that are easily treated that might be causing it, like a thyroid imbalance.
If you can summon up the discipline for it, it can be really helpful to try to become a lucid dreamer. I’m no expert in this and you can probably find lots of info about it on the web. the idea is that if you work at it, you can become active in your own dreams - you become able to recognize, while you’re asleep, that you’re having a dream, and become able to change the dream at will. I can do this enough to decide to wake up if I dream of flooding toilets.
You can also keep a diary of exactly what you’re thinking of before you lie down to sleep, which can help more than you might expect - most of us forget the details of what happens and what we’re thinking right in those minutes before falling asleep, and not forgetting can help a lot with crummy sleep.
I hope some of all that is helpful to you!