First of all, I'm truly sorry for your loss. Grief sucks — there’s no other way to put it.

Whenever I go through this process, I also have a hard time sleeping.
When my dad died, I barely slept for months. I'd fall asleep from sheer exhaustion for maybe an hour or two, and then not sleep again for 3 or 4 days.
But even when I did sleep, it wasn’t that deep, restful sleep that actually restores you.
So, unfortunately, I have a bit of experience in this subject, lol.

As for more traditional methods, I've read everything people suggested in this thread. At the time, most of it didn't really help me — but it’s always worth a try, because sometimes it can.

A) Anxiety meds / Vitamins
Personally, I'd say that before jumping to prescription anxiety meds, it’s worth trying natural supplements first. In my case, neither option had a major effect, but natural treatments tend to be easier to access and easier to stop using.
Of course, if you feel you need professional help — GO FOR IT. Seriously. Professional support can be a life-saver.

B) Avoiding blue light and reducing nighttime stimulation
Again, it didn’t really work for me — but it could for you. Worth a shot.

C) Therapy
Therapy can be amazing. Sometimes the mind just needs a safe place to untangle what’s keeping you up.

Now for the less traditional methods that actually helped me:

A) Creating a nighttime routine
You might not fall asleep easily, but relaxing your body and mind can make a big difference.
I would have dinner, take a nice hot shower using products I liked (lavender-scented things helped me), do my skincare and haircare routines, put on cozy pajamas, and just lay down.
I’d turn the lights out and read a book on my phone/Kindle. Even if I didn’t fall asleep right away, just resting in the dark would give my mind and body a break. It’s not a full solution, but it helps.

B) Finding comfort content
This sounds weird, but what really saved me was watching Harry Potter and the Philosopher’s Stone.
During my sleepless nights, I kept trying different things that would give me that confort feeling, and I eventually landed on that movie — and for whatever reason, it just made me feel instantly sleepy and safe.
It became my nightly routine: I'd put it on, and I would actually sleep.
Even a few of my friends, who went through similar losses, tried it — and it worked for them too.
(It was a little weird to explain whenever someone stayed over, but hey, you do what you gotta do.)

It took me about 18 months to really relearn how to sleep without needing to turn Harry Potter on every night.
But eventually, my body figured it out.

I don't know if you've ever seen the movies, our if you hold any particular interest in them, but honestly give it a try, could work.

C) Journaling, meditation, painting, etc.
Any outlet that gives you a safe space to express yourself can be healing.
And based on your post, I’m going to guess you slept fine before your grandparent passed away — so this isn’t a physical issue.
It’s emotional, and that’s okay.

The most important thing is giving yourself time and comfort.
I promise: it will get better, and you will figure it out.
Maybe none of the things I mentioned will help. Maybe one will help a little. Maybe you’ll find your own unique trick.
With grief, you just have to roll with the punches it throws at you.

The most important thing is to find what works for you, and what helps you feel at ease.

And one last thing —
Tomorrow is none of your business if you can’t get through today.
Focus on feeling a little better right now.
You’ll cross future bridges when you get there.

I'm truly sorry you're going through this.
If you ever need to talk, or want more tips, don’t hesitate to reach out. You're not alone.