Mr. Gaurav Arora,
There is no hard and fast rule about it. Either you can issue a warning letter for sleeping during duty hours, or you can issue a show cause notice and ask for his/her written explanation for such indiscipline.
Usually, three or more minor misconducts constitute major misconduct, but even the repetition of minor misconduct on three or more occasions does not warrant the termination of an employee's services.
For termination or dismissal of an employee, there have to be valid reasons such as fraud or indulging in an act of violence, etc.
Even when an employee is involved in the above act of indiscipline, certain procedures falling under the purview of the Industrial Dispute Act must be followed.
A brief summary of the steps involved is as follows:
1. Issue of a charge sheet asking for a written explanation.
2. Management not satisfied with the explanation.
3. Notice of a domestic inquiry to judge the gravity of the misconduct.
4. Appointment of an Inquiry Officer.
5. Inquiry Proceedings.
6. Submission of a report by the Inquiry Officer to the Management with findings.
7. Show cause notice to the employee clearly stating that they are guilty and requesting a written explanation.
8. Finally, the order.
I hope you now have a better understanding of it.