Can connect to Octocam but it reboots every few minutes


Web interface and ssh works for a while after rebooting but ever few minutes entire device reboots, then accessible again.
The Pi Zero is quite warm - could it be an overheating issue?


It could well be overheating and thermal shutdown.

You might want to log in over SSH, run “dmesg -w” and wait for it to shut down. See what messages you see before that happens.