Simple physical actions - most yoga-type postures can help relaxation. For example:
Either standing or sitting on the floor with legs stretched out in front - try to touch the toes. It doesn't matter how near or far one gets. Reach as far as possible, then stop, breathe out, and relax into that stretch. After a few seconds reach again, a little further, then stop and relax. Always be gentle.
Try the 'tree' posture. Stand upright and raise one leg so that the foot rests against the other knee (the raised knee out one side) and then slowly raise the hands above the head and circle to the sides and down breathing deeply.
The exact actions don't matter. If the body learns to stay where it is put, even balanced on one leg, it will more easily sit still when composed for prayer. A posture which is only used for prayer, such as kneeling or cross-legged on the floor, can come to prompt 'do not disturb' messages automatically.