Looks very much like a resonance. A video of this on a smoother road would help.
If it really is resonance, then it does not necessarily mean a mechanical problem with any of your components. Though it surely may lead to it. Resonance occurs when the frequency of periodically applied forces is close to natural frequency of the bike. Periodically applied forces are most likely originating from the wheel rotation. Natural frequency of the bike depends on a lot of factors and is hardly practical to calculate.
What you need to know is that the natural frequency of the bike will to some extent be impacted by any changes you make to the bike. Literally any change in any area of the bike could make it better or worse. Try a few things, but don't go too crazy about it. Resonance (aka speed wobble) can be quite bad to the point where rider cannot control the handlebars but it does look that bad in your case. It's not worth spending a lot of money on solving this issue unless it really impacts the quality of your rides.
I would try things in this order:
- Change tire pressure. Very first thing to try. Costs nothing. Do it.
- Change handlebar position either by flipping the stem or removing/adding spacers
- Change your front shock pre-load setting
- Remove your bar-ends. See if this makes difference. If it does, but you still want to ride with bar-ends, look at different model.
- Get another pair of tires (or maybe you already have it).
- See if you can borrow a fork from someone you know.
- See if you can get hold of a different handlebar (wider, narrower or different backsweep / rise)
- Get a different diameter wheels (ideally borrow from a friend rather than buy)
One of my bikes used to do exactly the same. Handlebar starts to osciallate even on the smoothest roads. But it only happens between 20 and 30 km/h and only when bike has panniers and front rack. It stopped doing so when I got rid of the panniers... Who could have guessed. I now use bikepacking bags
Some good reading on the subj: