if it keeps rebooting, most likely

1. adaptor issue (power supplied from adaptor is not enough to boot both the mobo + hdd)
2. mobo fan/casing fan issue (if your place is dusty, the fan bearing most likely gave up dy. Open up the casing, if your fan is not spinning, confirm sure your mobo overheat over time)
3. hdd issue (especially if you're not using surveillance HDD eg: skyhawk from SG, purple from WD)
4. mobo issue
5. Sata power/data cable faulty (very very VERY slim chance but kena before)

Occurrence frequency from 1 > 5

mobo = motherboard/main board

It'd help us to understand better if you can take a picture of the recorder, front panel and preferably the sticker (model) usually underneath the belly of the recorder.
Recorders without fan tend to have a higher warranty return rate for us.

Chances are if your recorder is more than 1 year old, most likely it's the adaptor issue.
Just double check if the adaptor is 12V 2A, also if the connector is proprietary like HIK recorders or just normal DC plug.

I'm assuming you're using IP cameras? 48V should be an adaptor for built-in PoE switch iinm.

TS is using an NVR for his IP Cameras + it's a unit with built-in PoE ports.
RM150 isn't going to cut it.

from experience, 48V adaptors rarely do spoil compared to those 12V ones.

In this case, since TS already showed the Toshiba HDD, suspect most likely the Toshiba HDD is acting up.

Also, that model is not for CCTV use. You can actually call your supplier and tell him you suspect hard disk issue. See if he's willing to bring a spare HDD to come over and help diagnose the issue?