I try to be as equanimous as possible, but then after a few minutes, I get so agitated that I have to open my eyes and move.
Any advice?
Stop trying.
The more you try, the less peaceful you will become.
So you're learning something.
You're learning that forcing things is a cause of suffering, is a cause of stress, trying to be equanimous.
You should accept the agitation.
And once you can accept the agitation, it won't be a cause for you to open your eyes.
You'll become bored with it, disenchanted with it, and you won't fuss or worry or be concerned by it.
Learn to meditate on the agitation.
Learn to meditate on your anger.
Meditate on your greed.
Learn to meditate on whatever comes up.
And you'll find that the hindrances arise less and less.
And you're able to be more equanimous as a result rather than as a practice.