Default [Q] My phone keeps restarting its self mid-boot - Not a rom/root issue.

I've been on holiday and while there my phone seems to have broke. It constantly restarts it's self - it gets to the HTC One splash screen and then will reboot again.

Most of the time I cannot get it into recovery as it will crash and re-start before it gets there, but I did manage a moment ago to get it to work for around two minutes and in that time I wiped the device - still having the issue though.

It's rooted with a custom rom, but I havent changed either of those elements in a good few months so dont think it's related.

I suspect this is a hardware issue and I'm boned, but wondered if anyone had a suggestion?