Not really painful. may be uncomfortable. Have had my exacerbated symptoms to shoulder after MRI of hand. they put my arm over my head and put my hand in first. I'd even called to make sure they could do the wrist and thumb. I just wasn't specific enough or smart enough to ask "Just how excactly are you going to position me for the MRI and how low will it last?"

You can't have any metal in your body, as the MRI is "magnetic resonance imaging," BIG MEGA magnets.

I'd ask for a round of PT. I would also ask the different PTs in your area what their technique would be and what their success rate is.

If not released now, or soon, it will only become more frozen.

Two frozen shoulders not good for the long haul...

Maybe around of steroids or injections to help.

Just some thoughts...