It's worth getting it checked out anyway due to 2 questions :
What's gone wrong ?
What's caused it ?
Answer to the first is : I can't start my car because the battery isn't giving the starter motor enough juice. If it's the type of starter I'm familiar with (took one apart, rebuilt it and it lasted longer than the car did*) then it's a pre-engager : It first moves a cog on to the flywheel and then the motor can turn the engine.
In this case, the cog won't quite be getting to where it needs to be the flywheel with that causing a nasty noise when the starter motor starts to properly spin.
What's caused it ?
This is where you want to get someone with tools to check it out, the battery could be flat due to :
It broke B) My Puma was ok one day, couldn't start the next. Reason - partial failure of the battery due to cold weather. It had enough juice for things like the radio but not enough to do anything with the starter.
It's not getting charged. My Rover had 2 (two!) alternator failures in 2.5 years, the first time was a "start one day, fail next" like the Puma's. That was a broken alternator though, without any warning lights appearing ...
I'm suspecting that you've had a stone or other missile come in and attack your battery, hence it needing lots of water to replace what may have leaked out of a hole. Either way, you need to know what's broken : Alternator or Battery. And for that you'll need someone with tools + knowledge ...
Something else as a symptom - if you've been hearing a screech on acceleration, that's a sign of the alternator belt slipping. That'll break the alternator after a while. Best to fix that before a £10 item breaks a £100 item ... (dunno prices, just saying scale!)
PS * "lasted longer than the car" - this isn't saying much because the car died in a pillar of flame a few months later :D