Hi Syed,
You will need to monitor the below list during the time interval you :
1. On SAP application side, ST22 & SM21.
2. On the OS side look for dev_disp in the work directory. You might have to check the one with old prefix as the new one would have logs from the last restart. In case of JAVA stack look for the dump files (hpprof.oom). You can use the memory analyzer to analyse this file and can also send it to SAP for further analysis
3. On the DB side check for the error logs
4. Also check for the Network disconnects with the help of your infrastructure team.
Thanks,
Manas