You might be suffering from having too many residual files or tempoary files clogging your system. Give your system a good cleaning: eliminate unnecessary programs, defragment your disc, check and...

Next time you re-boot, unplug your power supply for 20 seconds before starting up again. I can't explain why, but apparently some memory is retained so long as you are plugged in. Unplugging often...

Try replacing your battery (borrow before you buy).

I would narrow it down to two likely possibilities:
1. The battery
2. The charger.
Your best and simplest way to solve the issue is to borrow these two items from someone who has a similar, but...