No-name devices are typically very under-powered. It may be that the device is running out of RAM, causing a running app to close.
You could try booting into Safe Mode and testing an app that came preinstalled on the device. If the problem goes away in Safe Mode, it could be that some app you installed is causing instability as well. On most Android devices, while powered on, press and hold Power until the Power Off menu appears. Press and hold the Power Off selection until the Safe Mode prompt appears. Tap OK.
On certain devices, you have to power off, then power back on, but when you see the manufacturer logo appear, press and hold Vol Down until the homescreen appears.