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Ok, your symptoms are tell-tale... 100% classic for a lamp nearing end of life. If you can stand it, stop using the TV until you replace it. If the lamp shatters, you might be looking at a larger issue.
So, you just need a new lamp here, which is actually good news. I say "good" because this is totally normal (most folks get 18-24 months per lamp with normal use). The lamp is a consumable part, much like the light bulbs in your home... and just like a light bulb, the lamp is user-replaceable.
Go to dlplampsource.com or encompassparts.com and enter the TV's model number. The lamp should run you about $180 to have it shipped pre-installed in the housing. You'll be able to save $30-$50 by ordering the bulb by itself (no housing), but take my advice and spend the extra money; it'll make install much easier.
Please don't go to eBay or similar, and if the website has "cheap" in the title, it's bad news. Don't try to save money on this, trust me. Much less than the $180 I quoted you, and you're buying a counterfeit or factory reject, guaranteed. OK?
Your user's guide should have replacement instructions. Let me know if you get stuck.