Is it permissible to alternate between standing and sitting in supererogatory prayers when one feels tired?

A Muslim is permitted to perform supererogatory prayers, such as Tarawih, while sitting, even if they are capable of standing. However, the reward for one who stands is double the reward of one who sits, provided there is no excuse that makes standing difficult. This is based on the hadith: "Whoever prays standing, it is better; and whoever prays sitting, for him is half the reward of one who prays standing." There is no objection to sitting during a supererogatory prayer for whoever wishes to do so after having stood in it, and it is permissible to begin it sitting and then stand, or to begin standing and then sit. If one sits due to an excuse, then they receive the full reward.