Electric water heater switch won't stay in ON position

[lostinasia]

Is it similar to what I was dealing with here? I had a similar problem with the switch not staying on:

Electric hot water heater not working - any ideas?

As per title. Could just be our electric water heater has reached the end of its life and we need a new one. Could also be I’m a moron - and I’m certainly ignorant about home repairs. Or why not both? It came with the apartment, and we’ve lived here about 15 years. There’s a green and a red light, neither of which are currently lit. I’ve never noticed when they’re normally lit. Temperature gauge is reading low, at around 20 degrees. You’d think I’d be able to say what it normally is, but nope! …