I understand your problem a bit more now. I agree there is not so much difference between samatha and vipassana and one leads to the other and vice versa. But for me, anatta is not so much a reflection, contemplation or idea. In meditation it's more like a position I'm in. Or not in, as it's a position of 'me' not being there, me not involving in the meditation. If you have a sense of 'you' doing the meditation, 'you' contemplating anatta, you may miss this. As I said earlier, it is not like you decide to see things as anatta from one point on.
There can be more ways to remove restlessness, but for me they come down to the same thing. In a way it is accepting whatever is, which is also an aspect of metta. I'd say just accept restlessness, don't try to counter it with some contemplation if that contemplation blocks you somewhere else. If you can just embrace things as they are, there metta and peacefulness arise together. Ajahn Brahm calls it 'kindfulness'.
But I don't know for how long you have this obstacle. As you said, it started recently. I wouldn't worry about it too much because I don't think it will last long. The mind will find a way around it. A greater obstacle to generating metta is being a bit angry at yourself because you can't do it. I'd watch out for that one.
As for metta and compassion, try to find the most easy subject for you and make a sharp mental image of it before wishing it well. This works for me. It may also help to do some more kind acts in real life, remembering that the path is not only meditation. If you're stuck, meditation is not always the factor that's holding you back. For example, upholding the precepts fully is important as well.
Don't want to sound like a teacher or anything, so the above is just my experience and take what you think is helpful, leave the rest.