I'll voice with most of the other folks here -- get a new (and better)
power supply. About a year ago a family member with a PC from one of
the cheaper manufacturers had the exact same problem as you are
describing. We replaced the power supply with a beefier, named-brand
PSU, and the problem went away (and stayed away).

If you PC was a low-cost purchase, it is highly likely that it shipped
with a lame power supply. Not only is 200W small, it's also likely
that the PSU is cheap and flakey.