You have described acute onset disturbance in your father's behaviour which includes irrelevant talks, disturbed sleep, and aggression. You have also told that he has had 3 episodes of stroke in the past. Given the information provided, I suggest that your father needs early neuro-psychiatric evaluation. I suggest blood tests including blood electrolytes (Na+/K+), arterial blood gases (ABG), urea, creatinine, blood sugar, lipids; blood pressure monitoring and ECG with QTc interval and radiological test including MRI brain scan. You have told that he is on Quetiapine, which is used for controlling agitation and irrelevant talks and is also helpful in sleep.Do not delay. Your father needs proper detailed neuro-psychiatric evaluation and management. The underlying factors need to be evaluated and managed accordingly.