[Problem] Samsung Galaxy S5 SM-G900F restarts when opening text messages

Just yesterday my Samsung Galaxy S5 SM-G900F running Android 5.0 had a problem. When I open a text message, regardless of the sender, my phone automatically reboots. This doesn't happen all the time but it happens most of the time. At first I thought it was bad software so I did a factory reset but the problem is still there. I checked my battery and it's not bulging also. Nevertheless, I still used my phone even though it keeps on restarting and everytime this happens I carefully observed and what actions or situations might cause it and I came up with a finding. My phone only restarts when I open a text message in which the "Envelope" notification does not disappear on the status bar. Normally when you open an unread text message, the "Envelope" notification on the status bar should disappear since you already opened the message but mine doesn't disappear and after a few seconds my phone would restart. Can you help me on this? My phone is updated to the latest firmware provided for my region. Thanks in advance.