Stored procedure becomes slow every couple of days - sql

Question

I am facing an issue on SQL Server in which my stored procedure becomes slow after couple of days.
Below is the sample of my stored procedure.
Could this be a caching issue on the server side? Can I increase the server's cache size to resolve the problem?
Normally the stored procedure returns data in one second.
#START_VALUE int=null,
#END_VALUE int=null
#UID NVARCHAR(MAX)=null,
AS
BEGIN
SELECT
dbo.TABLE1.ID,
ROW_NUMBER() OVER (ORDER BY TABLE1.UPDATED_ON desc) AS RN,
CONVERT(VARCHAR(10), dbo.TABLE1.DATE, 101) AS TDATE,
CATEGORY = (
SELECT TOP 1 COLUMN1
FROM TABLE5 CT1
WHERE TABLE1.CATEGORY = CT1.CATEGORY_ID
),
TYPETEXT = (
SELECT TOP 1 COLUMN1
FROM TABLE6 CT1
WHERE TABLE1.TYPE = CT1.TYPE_ID
),
IMAGE = STUFF(( SELECT DISTINCT ',' + CAST(pm.C1 AS varchar(12))
FROM TABLE2 pm
WHERE pm.ID = TABLE1.ID AND pm.C1 IS NOT NULL AND pm.C1 <> ''
FOR XML PATH('')),
1, 1, '' ) INTO #tempRecords
FROM dbo.TABLE1
WHERE ((#UID is null OR dbo.TABLE1.ID = #UID )
ORDER BY TABLE1.UPDATED DESC
SELECT #count = COUNT(*) FROM #tempRecords;
SELECT *, CONVERT([int],#count) AS 'TOTAL_RECORDS'
FROM #tempRecords
WHERE #tempRecords.RN BETWEEN CONVERT([bigint], #START_VALUE) AND CONVERT([bigint], #END_VALUE)
END
GO
'

Answer 1

A few performance tips:
1) #UID is null OR dbo.TABLE1.ID = #UID --> this is bad because you'll have one execution plan when UID is null and when it's not. Build a dynamic sql query and you'll get 2 execution plans.
2) Update stats in a maintenance plan.
3) Check index fragmentation.
4) Try to do the same thing without using a temp table.
5) Try to avoid castings.