Is this something unusual or has anyone else experienced this? I'd like to note that this happens even during the daytime when I'm full of energy. It seems to happen every time I pray.
It seems disruptful to my prayer life. I do continue to finish my prayers and I pray throughout my entire day on a daily basis. I'm not sure if I'm thinking too much of it. Is it an attempt to get me frustrated and not want to pray, release of negative energy or stress and relaxed state with God?
This is not natural tiredness.
As you mention, you were full of energy no?
This is a spirit of weariness unique to when those who need to read God's Word or pray get an onset of spiritual fatigue (therefore the overflow manifests in the physical realm).
If you notice in scripture, Amalek attacked the stragglers in the Israelite's rear ranks who were tired and weary from their journey.
(Deuteronomy 25:17-19).
In the Israelite's battle with the Amalekites, Moses was holding up his hands and while his hands were raised.. they were winning but when his arms got tired and his hands were lowered... they would began to lose the battle.
(Exodus 17:8-16)
The Bible also speaks of becoming weary of doing good (Galatians 6:9) and the Lord Jesus says 'come to me all who are weary and I will give you rest' (Matthew 11:28)
This sometimes happened to my wife when I read the Bible to her, she began to yawn a lot.. it does gets better over time and with prayer.
'12 For we wrestle not against flesh and blood, but against principalities, against powers, against the rulers of the darkness of this world, against spiritual wickedness in high places.'
(Ephesians 6:12)
There's too many scriptures that speak of fatigue to think this has a natural cause.. fatigue not necessarily in the body but fatigue of the soul and spirit.