If Prayer Feels Like a Burden
Shaikh Muḥammad ibn Ṣāliḥ Al-ʿUthaimīn, may Allāh have mercy on him, said:
Prayer [feeling] heavy and burdensome on a person is an indication of some hypocrisy in his heart, so he must hasten to get rid of it.
Tanbīh Al-Afhām bi Sharḥ ʿUmdah Al-Aḥkām, p. 138.