This.
Also, can you afford to pay more? You can add voluntary contributions out of your net pay in to your workplace pension - if you have an Aviva account, it should allow you to set this up. The 8% total is a minimum payment - you can always pay more.
Alternatively, talk to your employer about whether you can do a "salary sacrifice" and pay in to your pension scheme gross (i.e. rather than pay £100 out of your net salary, you pay it out of your gross, saving you income tax and NI on it) -
Info
As others have said, you can transfer old pensions in to your new ones - you'd need to speak with the previous pension provider about transferring it to the new one.
The Chancellor announced in the Autumn Statement that it would be possible in the future to request that you keep the same pension when you change jobs, to avoid people having lots of pots all over the place.
Finally, on your Aviva login, you may find you can adjust how you want your pension saved. You may be able to choose your risk levels, so a higher risk might bring a higher return.
I am 44 and have less than you in my pot. It's something I'm working towards resolving, but I do have some other investments elsewhere.
Have a look at this website too - https://www.pensionbee.com/pension-calculator