[Closed] Mobile chucked a wobbler - help!

The battery has started going flat after a couple of days as it's knocking on a bit. Today it went flat so I charged it up as per normal. once it was fully charged I switched it on again and it said 'Start without Sim. accept. Reject. I rejected it a few times and it just switched itself off again. I split the phone, took the battery and the SIM out and gave them a clean and put them back in. Still came up with 'start without SIM'. In desperation I selected 'accept', everything is still on the phone but it can't see the SIM so doesn't work. Any ideas? Ta.