Shaking Handlebars

[Az]

I'm doing around 45-50, I lift my hands off the handlebars (to pull up my gloves as cold air was going up my jacket arm) and my handlebars start to shake side to side , they were only moving a very short distance, but quickly.. I typically shat myself, grabbed the handlebars and continued to ride.

The weird thing is, the bike wasn't moving it just continued in a straight line, I didn't even notice my handlebars were shaking until I looked down and saw them moving.

My questions are, what could be causing them to shake and is it something to be concerned about?

Thanks in advance, Az

[Islander]

Start with the simple stuff, tyre pressures, tyre wear, wheel balance.

[P.addy]

Wheel balancing or top box are my first checks.

Obviously if you don't have a top box, the balancing is the next one.

[bodger]

Some bikes are more prone to this than others.
Things like incorrect tyre pressures can cause this so this would be the first thing to check.
also having a top box can cause some instability.
Edit sorry lads beat me to it

[Az]

The bike did feel like it needed air, planned to put some in on my way back from work but forgot.
I just didn't think the problem would be related but I was clearly wrong lol
Well i'm out now, so i'll pop some air in on my way home and see what happens