Obstructive Sleep Apnea

Do you have any symptoms like snoring, interrupted sleep, unrefreshened sleep, morning headaches, daytime sleepiness etc, if yes it further supports the diagnosis.
It is a condition characterised by obstruction of upper airway especially during sleep due to lax airway and narrowing of airway due to obesity.
Basically, obstruction of upper airway leads to temporary stoppage of respiration, increased sympathetic drive and increased pulse rate. Also, other reason for pulse rate rise is deconditioning as you are not accustomed to activities.
Investigation
ENT examination if you have any symptoms of nasal stuffiness, recurrent tonsillitis to rule nasal causes of obstruction.

Thyroid function test
Lipid profile and sugar, hba1c
Vitamin D
Polysomnography which is sleep study to confirm the diagnosis and extent of disease, pressure of cpap needed.
In treatment, first thing weight loss. You need to have low fat, calorie diet in order to loose weight. Cure for this is weight loss.
Secondly, cpap which is mask and device, and pressure during inspiration and expiration during sleep in order keep your airways patent and avoid this from happening.
Also, regular exercises is very important. Chest physiotherapy and yoga will be helpful.