We previously reported on an issue in which the iPhone repeatedly reboots in the middle of phone calls. Afflicted users reported that the phone simply restarts anywhere from 1 to 5 to 10 minutes into calls.
Previously noted fixes include resetting network settings and restoring in DFU mode, as described in the 4 Rs of iPhone troubleshooting.
Anecdotal evidence now suggests that low memory, potentially due to misbehaving multitasking applications, may cause this issue. Readers using one of the many available memory monitoring apps for iOS report that the problem is much more likely to occur when free system memory drops below 10MB or so.
There are a few potential methods for dealing with this problem:
Manually close open apps. Simply close open apps by double-pressing the home key, then holding the app icon until it wiggles and pressing the small red circle. Albeit tedious, this method is generally effective.
Use a “memory freeing” app. Although the effectiveness of these tools is dubious, several readers have reported success in using them to avoid crashes. Options include Free Memory.