I'm in my 50s, I have a mixed bag - I took ill health retirement from the NHS so I already receive that pension.
I also have a SIPP and a small amount in NEST.
OK a SIPP is a 'self invested pension plan' you basically pay money into it and use it as a 'wrapper' for shares which you buy and sell. I had a couple of pensions from early in my life with very small amounts so I pooled them in the SIPP.
I WOULD NOT use this as my main source of income, It's more a bit of fun.
NEST is the government's scheme. Again I have only a small amount (hundreds not thousands) from a temporary job.
OK the advantages of starting a pension, even now.
Well the big one is tax, if you pay £75 into a pension the government will top it up to £100.
When you retire you can take part, or if it is a small pot, all of your money as a lump sum.
Also you don't have to take all of your pension at once and can still pay in even after retirement.
It might be better to think of your pension pot as an efficient savings account.
On suggestion I have seen if you are not sure you can put money away for a few years is to fill an ISA or other account and then at the end of a year transfer a lump sum, this means if you do need some money you can take it out of your ISA.
Nest is probably the simplest way to start a pension but it might not be the best option for you.
www.nestpensions.org.uk/schemeweb/nest.html