Hello and hope you are doing well.
Shuddering or restless in sleep could be due a sleep disorder. These disorders can be like obstructive sleep apnea, wherein during sleep there is an obstruction to air flow due to laxity of the throat muscles during sleep and this could cause restlessness. Hence for therapy CPAP (continuous positive airway pressure) is used to keep it patent. Another cause could be an entity called restless leg syndrome, where there is an odd sensation in the legs during sleep causing the individual to move, which relieves the sensation. These disorders can cause inadequate sleep leading to fatigue and daytime sleepiness. So, I would advise him to consult his primary care physician for further evaluation. He may then ask for a sleep study called polysomnography for further evaluation.
Hope this helped and do keep us posted.
Hi there ask your boyfriend to ask his Doctor to do a sleep study , were you say his breathing is limited , i would get it checked out , he may suffer from Sleep Apnea , Please take care........Bob